The Museum of the Osservatorio Vesuviano: inviting the public to explore the geoheritage of the world’s first volcano observatory

The Osservatorio Vesuviano (OV) is the oldest volcano observatory in the world having been founded in 1841 by the King of the Two Sicilies Ferdinand II of Bourbon. The historical building, located on the western slope of Vesuvius, hosts a museum with important collections of remarkable scientific, historical and artistic value, including pioneering instruments, rocks and minerals, photos and films of Vesuvius’ eruptions and many other memorabilia. Visitors discover this heritage through permanent exhibitions, and a multimedia path, across the history of Vesuvius and the origin of volcano monitoring. The museum lies within the protected area of Vesuvius National Park, established in 1995. The park’s network of trails allows visitors to enjoy the geodiversity of Somma-Vesuvius, whose activity has been intertwined with that of humans from Bronze Age to modern times, as testified by many important archaeological sites around the volcano, the most famous among them being Pompeii and Herculaneum. The “Grand Tour” was the cultural journey undertaken in the eighteenth century by European intellectuals, in which Italy was an essential destination; we consider the Museum of the OV an essential stop in a modern “Vesuvius Grand Tour”, a journey through the geological and archaeological heritage of Vesuvius territory. Since 2001, the OV is the Naples section of the Istituto Nazionale di Geofisica e Vulcanologia (INGV), which is primarily tasked with monitoring the three active volcanoes of the Neapolitan area—Vesuvius, Campi Flegrei and Ischia—through an advanced surveillance network.


Introduction
Volcano observatories are scientific institutions responsible for volcano monitoring and are committed to timely management of crises due to volcanic unrest, from precursory phenomena to the eruption itself and its aftermath. Observatories connect the volcanological scientific community with authorities in charge of civil protection (Lowenstern et al. 2022a, b). Over time, particularly in recent decades, many volcano observatories were established in response to renewal of volcanic activity, and, currently, forty-two countries worldwide host one or more volcano observatories (Lowenstern et al. 2022a). Of these observatories in the European Catalogue of Volcanoes (Barsotti et al. 2021), the Osservatorio Vesuviano (hereafter OV) at Salvatore Hill on Mt. Vesuvius (Naples, Italy; Fig. 1) holds a special place in history as the first volcano observatory in the world, founded in 1841 by the King of the Two Sicilies Ferdinand II of Bourbon. The main mission of the OV is well summarized by the words of one of its most important directors, Giuseppe Mercalli (Di Vito et al. 2014a), who in 1912 stated: "The Osservatorio Vesuviano is destined to reassure the surrounding populations during eruptions of great violence and to suggest the most opportune means to make them less disastrous" Since its construction and throughout its history (Fig. 2), the OV historical building has hosted many renowned scientists and has represented a cornerstone for the national and international scientific community (De Lucia et al. 2010). The observatory has been a place in which citizens have engaged with the geological history of Vesuvius territory, from the early twentieth century, with Mercalli's directorship (Nazzaro et al. 1995), to the present day (Martini et al. 2009;Nave et al. 2011;Avvisati et al. 2015a;Di Vito et al., 2014a and references therein). In modern times, the historical building became inadequate for carrying out increasingly complex surveillance activity (Nazzaro et al. 1995), and a new headquarter was built in the 1970s, close to the historical building. In the early 1980s, the OV Fig. 2 Timeline of the history of the Osservatorio Vesuviano from its foundation to the INGV headquarter was relocated to the city of Naples. The construction of the 1970s edifice to house the scientific activity offered the opportunity to set up a museum path in the historical building. The museum was further enlarged in 2000 with a multimedia path (De Lucia et al. 2010). Museums are dedicated to the education of the general public about different topics through dissemination and communication paths (Achiam and Marandino 2014). Effective communication and dissemination are of principal importance in the field of sciences (Stix and Heiken 2022). Often, volcano observatories use different kinds of communication and dissemination strategies (Snedigar et al. 2007;Brantley et al. 2019) that are fundamental tools to acquaint the population about natural phenomena and keep people updated about the hazards of ongoing eruptions. The OV, by virtue of its nearly 200-year history, combines modern communication tools, such as weekly/monthly surveillance bulletins released on social media and multimedia content, to traditional dissemination tools, such as museum exhibitions of historical collection of volcanological interest, telling the history of Neapolitan volcanoes. The knowledge of past volcanic history and its effect on the territory and communities contribute towards understanding what could happen in the future, in case of renewal of volcanic activity. The main topics in which citizens need to get involved are as follows (De Lucia 2014): What kind of eruption will occur? When will it take place? What should citizens do to mitigate their own risks and those of their families and livelihoods? In this framework, the Museum of the OV is committed to bringing citizens closer to these issues and, consequently, to increase general awareness about natural hazards and the consequences of living in an active, although currently dormant, volcanic area.

History of the Osservatorio Vesuviano: from the foundation to the INGV
Since the end of the seventeenth century, Vesuvius has attracted the interest of many scholars as reported by Ricciardi (2009). In 1694, the Catholic abbot Ignazio Sorrentino understood the importance of studying the activity of the volcano, in order to predict its behaviour, and recorded the activity of Vesuvius until his death in 1737. Throughout the eighteenth century, many scientists, such as Giovanni Maria Della Torre, Giuseppe Mecatti and William Hamilton, made observations and descriptions of Vesuvius eruptions (Ricciardi 2009). At the beginning of the nineteenth century, in a period of cultural and scientific ferment that had its roots in the Enlightenment, the need for a permanent seat to carry out direct observations prompted numerous scientists to clamour for the creation of a scientific institute for meteorological, magnetic and volcanological studies (Gasparini and Pierattini 1996). The request to establish an observatory was made by Teodoro Monticelli (1759Monticelli ( -1845, permanent Secretary of the Royal Science Academy of Naples, to the Bourbon monarchy in 1823. Monticelli was an attentive scholar of Vesuvius mineralogy and a collector of minerals, rocks and fossils. Noteworthy among his scientific works are the "Introduction to Vesuvius Mineralogy", cowritten with Nicola Covelli in 1825, and the description of the 1822 Vesuvius eruption (Brewer 2019). At first, Monticelli's appeal received little attention and his request was not welcomed. Things changed, however, in 1830 when Ferdinand II of Bourbon King of the Two Sicilies (1810-1859) ascended the throne. Ferdinand II was a passionate supporter of the sciences and he welcomed Monticelli's request in 1839, wishing for the observatory to become a reference point for observation and research on weather and volcanoes. Renowned physicist Macedonio Melloni, awarded with the Rumford medal (the Nobel Prize of the epoch) by the Royal Society of London in 1835, was appointed as the first Director by the King Ferdinand II (Gasparini et al. 1992;Gasparini and Pierattini 1996), who also financed the acquisition of meteorological and magnetic instruments. At first, Melloni proposed to build the observatory in Naples, at Riviera di Chiaia, ~16 km from the summit of Vesuvius, because he deemed that "Vesuvius lavas, acting as magnets, interfere with magnetic instruments" (Gasparini and Pierattini 1996). His proposal was rejected, probably due to complaints from many scientists who preferred that the headquarters be based on Vesuvius to carry out direct observations and measurements. Consequently, the observatory was built on Salvatore Hill, on the western slope of Vesuvius (Fig. 1). This site was easy to reach, far enough from the Vesuvius crater to be safe from eruptive hazards, and high altitude enough to avoid lava flows and allow for collection of meteorological data. The project was entrusted to the architect Gaetano Fazzini who designed a building in strict Neo-Doric style (Raia 2023). The construction of the observatory started in 1841 and ended in 1847. The inauguration of the new institute, named "Reale Osservatorio Meteorologico Vesuviano" (Royal Vesuvius Meteorological Observatory), took place on 28 September 1845 during the VII Congress of Italian Scientists in Naples, although the building was not yet complete (Gasparini and Pierattini, 1996). On this occasion, Director Melloni stated: "…in a century in which man is so successfully managing to tear from nature's bosom its deepest and most intimate secrets, it had become a matter of great importance and urgency to build an observatory for the express purpose of the day-to-day, practical study of meteorology and terrestrial physics" On 16 March 1848, the headquarters were handed over to Director Melloni, and the scientific activity of the observatory officially started. A few months later, Melloni was dismissed from the office of Director for being suspected of having liberal political ideas. After his dismissal, the OV fell into a state of abandonment until 1856 when Melloni's former student Luigi Palmieri, professor of Logic and Metaphysics and then Terrestrial Physics and Meteorology at the University of Naples, was appointed Director until his death in 1896. Palmieri raised the fortunes of the observatory and had a meteorological tower built to house some of the instruments purchased by Melloni. He implemented, for the first time, a scientific surveillance network featuring instruments he himself devised (Borgstrom et al. 1999), such as the famous Palmieri's electromagnetic seismograph, that could record seismic signals on paper (see the "The historical collections: a scientific and cultural heritage" section). Palmieri's pioneering observations of harmonic tremor due to magma degassing demonstrated the relation between seismic activity (even low-energy activity) and volcanism (Borgstrom et al. 1999). After the 1872 eruption, when lava flows surrounded Salvatore Hill, the government installed a telegraph to facilitate communications (Casertano 1999). Vesuvius' activity was documented in quasi real-time by means of telegrams and bulletins to local press. Thanks to his remarkable scientific achievements, Luigi Palmieri is one of the few Italian scientists after whom a lunar crater is named. After Palmieri's death, Eugenio Semmola became acting Director. In 1903, the geologist and volcanologist Raffaele Vittorio Matteucci was appointed Director and held the office until his death in 1909. Matteucci inherited the observatory in poor conditions due to neglect following Palmieri's death and to lack of funding resources. Matteucci witnessed and described the violent 1906 eruption of Vesuvius (De Lucia et al. 2006) that severely damaged the observatory, with the fundamental contribution of Frank Alvord Perret, an American inventor and engineer who was passionate about volcanology (Belkin and Gidwitz 2020). After a brief period (1909)(1910)(1911) in which Ciro Chistoni was acting Director, the directorship passed to the geologist and Catholic abbot Giuseppe Mercalli in 1911. Mercalli's scientific activity ranged from the study of glacial soils (in the early years) to seismology and volcanology; an exhaustive description of his scientific activity is reported by Di Vito et al. (2014b). His detailed studies of several violent earthquakes (Cubellis 2014;Pino and Milano 2014), including Casamicciola (Ischia Island, 1883), Andalusia (Spain, 1884), Liguria and Piemonte (Italy, 1887), Calabria (Italy, 1905 and1907) and Messina (Sicily, 1908), led him to evaluate the Rossi-Forel seismic scale (in use at that time) inadequate, so he developed his famous seismic intensity scale which is based on the destructiveness and damage produced by an earthquake . In its first formulation published in 1897, Mercalli's seismic scale included ten degrees of intensity indicated by Roman numerals (I = instrumental; X = very disastrous). Following the 1908 Messina earthquake and at the suggestion of the geophysicist Adolfo Cancani, who also coupled values of ground acceleration to each degree, Mercalli added two more degrees (XI = catastrophe; XII = great catastrophe) to his scale. In the field of volcanology (de Vita et al. 2014;Nave and Siniscalchi 2014;Siniscalchi and Nave 2014;De Lucia and Ricciardi 2014), Mercalli studied the eruptive activity of Etna (Island of Sicily), La Fossa cone on the Island of Vulcano, Stromboli (Aeolian Archipelago) and Vesuvius and proposed a unitary classification scheme of volcanic eruptions. He scrutinized the relation between strong earthquakes and volcanism and suggested, based on his studies on Ischia Island, that earthquakes in volcanic areas should be regarded as "failed eruptions". As Director of the observatory, Mercalli immediately had to face many difficulties related to the extensive damages caused by the 1906 eruption. In his notes, regarding the state of the observatory in 1911, Mercalli reported (Russo et al. 2014): "…books resting on a sofa, instruments and collections in a ruined closet. Wall are damaged and the main entrance is destroyed so that wind, rain and stray dogs had free access. The building was in a such bad hygienic conditions to make it uninhabitable…almost all meteorological instruments are broken; no seismic instruments were working; the library and the collection of Vesuvius products were in disorder and not catalogued, lastly instruments for volcanological studies were unusable or missing" Thanks to his tenacity, Mercalli managed to obtain funding from the government with the aim of renovating the observatory and initiating an ambitious volcano monitoring program based, for the first time, on a multidisciplinary approach encompassing observing with instruments, building a new seismic surveillance network and carrying out systematic field measurements. In the implementation of this program, Mercalli was assisted by Alessandro Malladra, his former student, who succeeded him as Director a few years later. This new surveillance program became operational in May 1913, and in the same year, intracrater activity resumed at Vesuvius. Mercalli proposed, for the first time, the institution of an Italian Volcanological Institute, of which the OV would have been a cornerstone. Tragically, Mercalli did not reap the benefits of his work due to his untimely death (Molisso et al. 2014), which occurred on 19 March 1914. Mercalli's idea of establishing an Italian Volcanological Institute was driven by his will to advance the volcanological research and the fact that a new volcanological institute, to be opposed to the OV, was founded in Naples by the German volcanologist Karl Gottfried Immanuel Friedlander (Russo et al. 2014) in a period in which volcanological and petrological studies were flourishing. In this climate of scientific and cultural ferment (Cubellis et al. 45 Page 6 of 21 2017) driven by the competition between the two institutes (Russo et al. 2014), the studies of another renowned scientist, the Swiss volcanologist Alfred Rittmann, further contributed to the development of the modern volcanology in Naples. Rittmann was employed at the Friedlander Institute, and his studies mainly focused on the evolution and differentiation processes of magma feeding Somma-Vesuvius' eruptions and on the formation of the Campi Flegrei caldera and the island of Ischia (Ippolito and Marinelli 1981). After a very brief period in which Alessandro Malladra was acting Director, in 1915, the management of the observatory was again entrusted to Ciro Chistoni, one of the most renowned geophysicists of the time, and then to an Italian Volcanological Committee headed by Chistoni himself. The management of the OV was entrusted to the volcanological committee until 1926. At the end of 1926, the committee was relieved of office, and Alessandro Malladra was appointed Director keeping the office until 1935. Malladra had previously been Mercalli's assistant and made direct observations of the eruptive phase of Vesuvius that started on 5 July 1913. This phase was characterized by intracrater activity and the progressive growth of a small cone that in 1928 exceeded the crater rim, culminating in an eruption in 1929. Malladra continued his observations as Director of the OV, making measurements of the cone and lavas filling the crater (Redondi 2011). From 1936 to 1970, the Director was Giuseppe Imbò, professor of Terrestrial Physics at the University of Naples. He witnessed and described the last eruption of Vesuvius that occurred in 1944. The observatory was requisitioned by the Allied Command during the World War II to use the meteorological tower for radio communications. With the Allied Command's interference preventing thorough monitoring of Vesuvius' activity, Imbò foresaw the beginning of the 1944 eruption with only the aid of a seismograph and direct observations (Chester et al. 2007). After Giuseppe Imbò's retirement, the directorship passed to Paolo Gasparini, professor of Terrestrial Physics at the University of Naples, from 1971 to 1983. Gasparini was also President of IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior) from 1991 to 1995. During his tenure, the OV was called upon to manage the emergencies related to the 1970-1972 Campi Flegrei bradyseismic unrest and the 1980 earthquake in Irpinia (Castellano et al. 2002). Emeritus professor of Geophysics at the University of Naples Giuseppe Luongo headed the OV from 1983 to 1993, managing the emergency of the 1982-1984 Campi Flegrei bradyseismic unrest during which about 40,000 people were evacuated from Pozzuoli (Barberi et al. 1984). Emeritus professor of Geochemistry Lucia Civetta was Director between 1993 and 2001; she was the last Director of the OV in its form as an independent research institute.
In 2001, the OV officially became the Naples section of the Istituto Nazionale di Geofisica e Vulcanologia (INGV), a national research institute in charge of seismic and volcano monitoring in Italy and committed to provide information to the Italian Civil Protection (Dipartimento di Protezione Civile (DPC)), funded by the Italian Government (Margheriti et al. 2021). In addition to Naples, INGV has headquarters in Milan, Pisa, Bologna, Rome, Grottaminarda, Palermo and Catania. Although the OV is now part of the INGV, it has kept its historical name by virtue of its long history and scientific contribution to the birth and development of modern volcano monitoring. The headquarter and all facilities of the OV are currently located at Fuorigrotta, within the city of Naples. Since 2001, the directorship has been entrusted to Giovanni Macedonio (2001-2007, Marcello Martini (2007-2013), Giuseppe De Natale (2013 and Francesca Bianco (2016-2022. Since August 2022, the Director has been Mauro Antonio Di Vito.

The Museum of the Osservatorio Vesuviano
The museum complex of the OV is arranged around a church and a hermitage (Eremo del Salvatore) that predate the historical building of the observatory on Salvatore Hill (Fig. 3). The complex is formed by two main buildings: the historical building, built in 1841-1847 and located just uphill of the church, with an adjoining historical garden housing various plant species, and a three-floor, 800 m 2 modern structure, built in the 1970s. Overall, the two buildings cover an area of 2000 m 2 . The complex also includes a guesthouse.
The historical building hosts the museum with collections of scientific, cultural and artistic interest, dating back to the beginning of the nineteenth century. There are scientific instruments, rocks and minerals, antique books (some of Fig. 3 Construction of the Osservatorio Vesuviano on the Salvatore Hill (c. 1843, unknown artist). The observatory is between Vesuvius (in background) and a church with an adjoining hermitage (in foreground) that predate the observatory which date back to the sixteenth century), old geological and geomorphological maps and models. There are also busts, portraits, photos and films of historical eruptions of Vesuvius, gouaches and vintage prints of the volcano, lava medals, ashes and various samples of the historical eruptions, in addition to recordings on smoked paper of seismic activity from 1915 to 1970, and the apparatus for smoking the paper as well. Original furnishings, such as the Director's office, are preserved as they appeared in the early twentieth century (Fig. 4).
The historical building is spread over three floors. The façade (Fig. 5) looks southwards and involves two floors with separate entrances, located at the ground and first floors. The monumental entrance at the first floor comprises a colonnaded porch reached by a staircase in lava stone with two side ramps. The façade, faced with blocks of piperno and lava, encases six arcades with large windows framed in plastered bricks. The top-floor façade is also in plastered bricks, with corners made of lava blocks. It displays two sundials that indicate solar time and the months of the year. A stone slab in the centre bears an inscription recording the foundation of the observatory at the behest of King Ferdinand II of Bourbon (Fig. 5). Large terraces with panoramic views were used for external observations of volcanic phenomena (Fig. 6). Indoors, the first floor has a hall, accessed from the monumental entrance, three rooms dedicated to William Hamilton, Teodoro Monticelli and Giuseppe Mercalli, the Director's office and the prestigious octagonal room (Fig. 7), used by Macedonio Melloni to house magnetic instruments and, originally, intended to hold the busts of the King Ferdinand II carved by the sculptor Tito Angelini (1804-1878). On the second floor is the Great Hall, now the Palmieri Hall ( Fig. 8), ornamented with six "shrines" framed by pilasters with capitals and decorated pediments featuring cornices and inscriptions in gypsum plaster. The ceiling decorations were entrusted to the painter Gennaro Maldarelli (1795-1858) who used the technique of oil on unprepared canvas. The subjects of the central paintings are as follows: Minerva, the goddess of science, crowning Prometheus, with various cherubs in attendance, Aeolus commanding the winds and the Forge of Vulcan. These are flanked by paintings of a whirlwind and a waterspout. Altogether, the ceiling art represents the four elements, joined under the ellipse of a rainbow, framing the central mythological scene in which Minerva, crowns Prometheus, dispenser of the fire of knowledge. The subject is likely an allegorical homage to King Ferdinand II's benevolence towards the Arts and Sciences of the Earth (Fig. 8).
The museum, which targets audiences of any cultural background although it is visited mainly by school groups, presents a journey through the history of volcanology and volcano monitoring from its origins to the present day (De Lucia et al. 2010;Avvisati et al. 2015b). The main aim of public outreach activities is to improve knowledge, awareness and understanding of volcanic risk knowledge and awareness among people living in high volcanic risk areas (De Lucia et al. 2004De Lucia 2007. Traditional permanent exhibitions take people back in time through the narration of the historical eruptions of Vesuvius and scientific instruments that come from a distant past, but which were innovative and cutting-edge for the time. Vintage photos and films tell of the effect of the Vesuvius eruptions on people's lives and territory and allow the general public to understand what it means to live in an active volcanic area and what volcanic risk is. The museum shows how local populations suffered the consequences of volcanic eruptions and hazards through time with two rooms dedicated to two eruptions of Vesuvius, the famous AD 79 "Pompeii" eruption and 1944 eruption (De Lucia et al. 2010). Masterpieces of art and craftsmanship, such as gouaches and lava medals, demonstrate how local communities have benefited from living close to a volcano in

The historical collections: a scientific and cultural heritage
The museum's collection of artefacts and archives of geovolcanological, scientific and cultural interest deserve a detailed description. These memorabilia tell the history of the oldest volcano observatory in the world and highlight the twofold role of Vesuvius in this history: a catalyst for cultural and artistic development with effects throughout Europe and an engine of scientific and technological progress in the field of Earth Sciences and volcano monitoring in the last three centuries.

Collection of rocks, minerals and volcanic ash from historical eruptions of Vesuvius
The collection includes at least 250 samples of ash ( Fig. 9), and many lava samples, lapilli and bombs from Vesuvius' activity since the 1822 eruption, the volcano's strongest eruptive event of the nineteenth century. Many of these samples were collected by Teodoro Monticelli, Arcangelo Scacchi and Alessandro Malladra. Vittorio  The octagonal room at the first floor seen from above. The display cases set in the walls exhibit rocks, minerals and ash samples in glass jars Matteucci collected the complete sequence of ash from the 1906 eruption. The ash samples are preserved in glass jars accompanied by original tags reporting the date of the eruption and sometimes the site of sampling. The museum also owns many mineral specimens from Teodoro Monticelli, one of the most important collectors of Vesuvius rocks and minerals. The Monticelli collection comprises 100 specimens, but unfortunately, due to the occupation of the OV by Allied troops during World War II, much of this material has gone missing. In 2011, Mariano Carati, a passionate private collector, chose to donate his distinguished and historic collection to the Museum of the OV (De Lucia and Russo 2011). Carati's collection includes over 250 specimens of rare minerals, partly donated by Antonio Parascandola. Most of these minerals were observed and classified for the first time on Vesuvius (Russo and Punzo 2004). The collection is arranged according to the depth that the minerals formed within the volcanic system, from magma chamber to shallow hydrothermal system and surface fumaroles.

Lava medals
Lava medals represent an example of how the product of a natural event, like a volcanic eruption, can be transformed into a masterpiece of art. This collection, whose catalogue has been revised by Antonio Nazzaro in 1999, includes 76 lava medals, 13 samples of lava containing coins and buttons, 5 metal punches and a coin with Arabic engravings Uzzo et al. 2013). Most of the medals, 50 items, were donated to the observatory by Alessandro Malladra. The production of medals was strictly related to the activity of Vesuvius and availability of fluid lava as raw material. Production of the medals was limited to the effusive eruptions and stopped during explosive events or periods of dormancy. The making of medals took place directly on the volcano, near an eruptive vent from which the lava flowed placidly. The proximity to the vent was due to the need for very hot, fluid and, therefore, easily mouldable lava. Two metal punches, representing the front and back of the medal, were immersed in the fluid lava, taking a sample on which engravings bearing writings or images were imprinted. After cooling, the result was a lava disc with incisions surrounded by a scoriaceous crust due to the lava sticking to the metal punches. The image of Vesuvius, depicted with a small plume typical of its activity until the 1944 eruption, was constantly represented in the iconography of lava medals. The medals were mainly made to pay homage to great personalities from contemporaneous history or characters from mythology or to seal the love between two lovers. Medal production flourished in the nineteenth and twentieth centuries and stopped definitively in 1944 when Vesuvius entered a state of quiescence. According to the revised catalogue of Antonio Nazzaro, the oldest medal and the most recent medal date back to 1819 and 1940, respectively. A complete catalogue of the collection is reported in Uzzo et al. (2013) and includes the whole description of the lava medals, their context and recto-verso images.

Gouaches of Vesuvius
Since the eighteenth century, Vesuvius was among the artists' favourite natural subjects thanks to its frequent and spectacular eruptions. Many gouaches were created as souvenirs for travellers of the European "Grand Tour" (Sigurdsson 2015). The French term "gouache" ("guazzo" in Italian) indicates a quick-drying painting technique based on the use of opaque water colours (Ford 2018). The OV's collection of gouaches, which it has owned since 1912, depict Vesuvius and its eruptions that occurred between 1819 and 1834. Three are by Odoardo Fischetti (Fig. 10), one by Luigi Gentile and the rest by unknown artists. The gouaches show many volcanic phenomena and changes of Vesuvius morphology as a consequence of these eruptions, adding a scientific value to their artistic value.

The historical library
The historical library's volcanological books include 10 volumes from the sixteenth century, 64 volumes from the seventeenth century and 96 volumes from the eighteenth century. The seventeenth-century books deal mainly with topics related to the 1631 eruption, while the eighteenthcentury books are compendia of Vesuvius history by various writers, such as Serao, Sorrentino, Mecatti, De Bottis and Ascanio Filomarino. The most valuable book is undoubtedly that of the Jesuit Athanasius Kircher, Mundus Subterraneus, dating back to 1668; it describes the state of Vesuvius and Etna as well as the main concepts of natural history.

Geological and geomorphological maps and models
This collection includes the first volcanological map of Vesuvius, drawn by Johnston Lavis between 1880 and 1888, and surveys of the changes in the Vesuvius cone following various eruptions, conducted by Raffaele Vittorio Matteucci, Giuseppe Mercalli and Alessandro Malladra (Ricciardi 2009). The collection also features numerous 3D models of Vesuvius, Campi Flegrei, Santorini, Stromboli, Etna and Fogo. The oldest models date back to 1875 and 1878 and represent Mt. Etna and Vesuvius on a zinc sheet electroplated with copper.

Vintage photos and films
This collection contains a large number of photographs and films shot between 1865 and 1944, documenting eruptions of Vesuvius and other Italian volcanoes and the scientific activity of the observatory. The oldest film in the archive is even the first film ever made of an erupting volcano, shot by the Lumière Brothers in 1898, only two years after the invention of the cinematograph. The short film records the formation of Colle Umberto (1895-1899). Another rarity is a film of the catastrophic 1906 eruption made by the Troncone Brothers and donated to the OV by Giovanni P. Ricciardi. The 1906 eruption is also the subject of a series of photographs taken by Frank Alvord Perret. Monitoring activity was documented as well, such as repeated descents into the crater (Fig. 11) for sampling gases and/or measuring temperature following the 1906 eruption. The photographs also show the techniques and equipment used to carry out these activities. The most recent film, which documents the 1944 eruption, was shot and donated by the Allied Forces. The collection is completed by numerous photographic plates and negatives, the oldest dating back to 1865, showing Vesuvius, Etna, Stromboli and Vulcano (de Vita et al. 2022).

Recordings on smoked paper of Vesuvius seismic activity from 1915 to 1970
The paper seismic recordings have notable scientific and historical value because they document the volcano seismic activity from 1915 to 1970. The paper was smoked with a special equipment and mounted on rollers that rotated at a constant speed. Nibs connected to seismographs etched the carbon black and wrote the seismic signal on the smoked paper. The collection also includes the equipment used to smoke the paper.

Scientific instruments
The pioneering scientific instruments belonging to the OV's collection illustrate the scientific progress made, throughout the nineteenth century to the beginning of the twentieth century, in the field of volcano monitoring. The collection includes seismological, magnetic, geodetic, geochemical and meteorological instruments used for surveillance at Vesuvius. The seismographs are especially noteworthy, with devices designed by Luigi Palmieri, Ascanio Filomarino, Emil Johann Wiechert, Guido Alfani and Giovanni Agamennone, all in excellent conditions.

The Palmieri seismograph
Palmieri built several scientific instruments (Borgstrom et al. 1999), essentially meteorological or seismological, of which the Palmieri seismograph is undoubtedly the most famous, existing in fixed and portable versions (Fig. 12). This instrument made it possible to record earthquakes on paper. The first model was built in 1856, generating great interest in the international scientific community. For this invention, Palmieri received a prize of about 5000 US dollars from the University of Boston and the gold medal of the Lisbon Academy. One of the first specimens was bought by the central meteorological institute of Tokyo, at the request of the Japanese government. Palmieri installed two copies, one in the Cabinet of Terrestrial Physics of the University of Naples and the other in the Great Hall of the Observatory, now the Palmieri Hall. The original idea was to interface a traditional seismoscope with a telegraphic device he had modified, so as to create the first electromagnetic seismograph. The seismograph was used until the end of the nineteenth century, when it was replaced in the various Italian observatories with mechanical seismographs.

The Filomarino seismograph
In 1794, a violent and spectacular eruption of Vesuvius occurred that destroyed the town of Torre Del Greco. After the eruption and putting into practice the knowledge acquired from the 1783 earthquake that occurred in the Calabria region (southern Italy), Ascanio Filomarino constructed an instrument called "vertical pendulum seismograph" which was able to indicate the exact instant of a seismic event and record it graphically (Luongo and Nazzaro 1990). This seismograph consists of a long pendulum fixed to a wall, which terminates in a spherical mass, with a pencil fixed in its lower part. The pendulum oscillation during an earthquake is traced over a paper disc about 8 cm in diameter, placed on a cylindrical marble base marked with compass points. Connected to the mass were three bells, which functioned as alarms, and a semi-rigid strand of horsehair that blocked the rocker arm of a clock. Ascanio Filomarino described its function thus: "this seismograph gives the strength, direction and time of the beginning of an earthquake, so even if I am not at home when an earthquake occurs, I will find it all recorded on the paper mentioned... I have described this machine so that in the Capital (Naples) and in the towns near the volcano it may be used together with a precise atmospheric electrometer. By observing these together with the external signs of the volcano, it may sometimes be possible, if not to clearly foresee a new eruption, at least to conjecture it".

The Wiechert seismographs
The seismographs devised by Emil Johann Wiechert (Schröder and Treder 1999;Mulligan 2001) provided a way to investigate the Earth's interior and soon became a standard equipment in many observatories, including the OV. Wiechert's seismographs recorded both the horizontal and vertical components of ground movements during a seismic event. The main feature for measuring horizontal ground motion is an inverted vertical pendulum weighing 200 kg, whose centre of gravity is 100 cm above the centre of rotation. It is suspended within a base structure that has three supports through which the apparatus makes contact with the ground. Connected to the pendulum are two arms that, by means of a delicate system of levers, transmit ground movements to two pens that write on strips of smoked paper mounted on rotating drums. The part of the seismograph that measures the vertical component of motion is composed of a horizontal pendulum maintained in equilibrium by the elastic force generated by a spiral spring that counteracts the force of gravity. The movement of the mass is dampened by a compressed air system.

The Alfani orthoseismograph
In 1913, Guido Alfani supplied the observatory with a type of long-period seismograph for recording vertical ground movements. The orthoseismograph is composed of a 150-cm iron rod at the end of which there is a mass of 200 kg made of lead discs. At the other end, two large screws act as a fulcrum, and large springs serve to apply a return force that keeps the mass in equilibrium position. When an earthquake occurs, the vertical movements of the ground cause the mass to oscillate, and this movement is transmitted mechanically to a pen nib which writes on smoked paper to produce a seismogram. Two levers transmit the movement of the mass permitting the amplification of the signal by a factor of 50 to about 300, so that even minimal displacements of the mass are detected. The recording apparatus consists of a drum 1 m in circumference overlain by smoked paper, which is made to rotate by a clockwork mechanism wound up by a crank. The orthoseismograph is dampened by an oil-based system.

The Agamennone seismograph
Giovanni Agamennone left a seismographic archive of great scientific value, as his instruments recorded a great deal of precise information about many seismic events (Louderback, 1948), including the 1908 Messina earthquake. The Agamennone seismograph was built in the workshops of the Central Office for Meteorology and Geophysics in Rome and installed in 1913 by Alessandro Malladra, assistant to the OV's director at that time, Giuseppe Mercalli. This seismograph consists of a pendulum 16 m long, with a mass of 600 kg, that is insensitive to vertical movements and is thus able to measure in a targeted manner the horizontal components of ground movement. The mass is suspended from a fine steel cable anchored to the third floor of the building and protected by a tube 10 cm in diameter. The pendulum's natural period is 7.5 seconds, and it amplifies the actual movement of the ground by a factor of 10. The signal is recorded by two pen nibs on smoked paper wrapped around a rotating drum, which trace the two horizontal components of the motion. Two additional fixed pens register parallel reference lines.

The OV surveillance network and monitoring activity of Neapolitan volcanoes
The OV, through a 24/7 surveillance activity and real-time seismic and volcano monitoring performed in a control room based in Naples, watches over the volcanoes of the Neapolitan area. In the OV surveillance room, two people are on duty 24 hours every day and are responsible for earthquake location and magnitude (Md) determination. A group of four specialists (a seismologist, a volcanologist and two IT technicians) are always on call (Margheriti et al. 2021). When an earthquake occurs, the communication threshold for volcanic areas, down to 100 km of depth, is Md ≥ 2.5 except for Ischia and Campi Flegrei for which the threshold value is Md ≥ 1.5 (Margheriti et al. 2021). The operating procedures to provide information to the DPC and general public follow specific protocols (Cirillo and Peluso 2020;Margheriti et al. 2021). The communication to DPC of the occurrence of a seismic event occurs by telephone, SMS (Short Message Service) and email. The information is also published on the INGV blog and released on social media for the general public. The communication time of the preliminary parameters (location and magnitude), calculated automatically, is expected in 2 minutes (rapid calculation) and 5 minutes (final calculation). Within 30 minutes, the seismologist in the control room analyses the signals and provides the verified parameters. On average, the communication of the revised parameters is provided 12 minutes after the earthquake occurrence (Margheriti et al. 2021).
The Neapolitan volcanic area contains three dormant volcanoes with different morphologies and histories: Somma-Vesuvius, Campi Flegrei and Ischia Island. In this section, the history of each volcano is briefly described along with the current surveillance network of each volcano. Furthermore, the state of each volcano at the time of writing (May 2023) is reported according to the levels of alertness defined by the DPC. The lowest level (green) indicates no significant changes in monitored parameters (quiescence). If anomalies are detected in the monitored parameters and those anomalies progressively increase, the alert level may rise to "attention" (yellow), "pre-alarm" (orange) and "alarm" (red). Red is the highest level and necessitates the complete evacuation of the most hazardous zone (red zone) according to the emergency plan (Carlino 2021).

Somma-Vesuvius
Somma-Vesuvius is one of the world's most famous volcanoes. It is a composite volcano formed by a geologically young (<2000 years) volcanic cone, Vesuvius (1281 m.a.s.l.), grown within a caldera representing the remnant of an older stratovolcano, Mt. Somma (1132 m.a.s.l.). A sequence of four Plinian eruptions progressively reshaped and dismantled the Somma edifice during a poly-phased, caldera-forming stage that lasted twenty millennia (Cioni et al. 1999;Sbrana et al. 2020). The oldest of these Plinian events occurred 22 ka BP and was named "Pomici di Base", followed by the 8.9 ka "Mercato" eruption, the 3.9 ka "Avellino" eruption and, lastly, the famous AD 79 "Pompeii" eruption. This stage resulted in a quasi-elliptical, E-W elongated caldera whose major and minor axes are 4.9 and 3.4 km long, respectively (Bertagnini et al. 1998;Cioni et al. 1999). Following the AD 79 eruption, the renewal of the activity within the caldera led to the discontinuous growth, in alternating constructive and destructive phases, of the Vesuvius cone. The volcano awoke violently in AD 472 ("Pollena" sub-Plinian eruption, Sulpizio et al. 2005Sulpizio et al. , 2007 and again in 1631 (Rosi et al. 1993;Rolandi et al. 1993). Between the 1631 eruption and the most recent eruption in 1944, Vesuvius was characterized by open conduit, semi-persistent activity, from central and lateral vents, mainly with mild explosive eruptions and many lava effusions (Arnò et al. 1987). Since 1944, the Vesuvius conduit remains obstructed, and the volcano is in a state of quiescence. The activity of Vesuvius is monitored by the OV through the observation of geophysical, geochemical and geological parameters. Various instruments are installed on Vesuvius' slopes for continuous monitoring of seismicity, ground deformation and gas emissions from the ground and the fumaroles. The permanent seismic network includes 18 sites equipped with short-period and/or broadband seismic stations. The geodetic measurements are carried out through a GPS network composed of 8 stations, a tiltmeter network composed of 8 stations and a tide-gauge network. Discrete measurements of ground level and gravity measurements are carried out through regular levelling campaigns. Monitoring of thermal anomalies is carried out using a permanent network of infrared thermal cameras installed along the Vesuvius rim, supplemented by monthly measurements with mobile thermal cameras and thermocouples. Fluid geochemical surveillance is carried out by continuous measurements of the CO 2 flux from the ground, temperature of the main fumarole and the temperature gradient with multi-parametric stations, installed along the crater rim and within the crater floor. Periodic sampling of the fumaroles active along the crater rim and floor is carried out as well as measurements of the CO 2 flux and temperature gradients in selected fixed sites (Di Vito 2021). In its current state, Vesuvius has a hydrothermal system that feeds some fumaroles inside the crater (Ricco et al. 2021). It is characterized by a modest seismicity of a few hundred small earthquakes per year. The alert level at the time of writing is green.

Campi Flegrei
Campi Flegrei (CF) is a volcanic field comprising many vents, which formed tuff cones, tuff rings, maars and lava domes. Its main structure is dominated by a nested resurgent caldera (Orsi et al. 1996;Orsi 2022) associated with the ~40 ka Campanian Ignimbrite (CI) eruption and the 15 ka Neapolitan Yellow Tuff (NYT) eruption. The activity younger than 15 ka was intense and clustered within the NYT caldera in three epochs (Di Vito et al. 1999;Smith et al. 2011) of volcanism, characterized by magmatic to phreatomagmatic and minor effusive eruptions, with repose periods never exceeding 70 years, separated by long periods of quiescence during which well-developed paleosols formed. Epoch I (15-10.6 ka) includes at least 32 eruptions, Epoch II (9.6-9.1 ka) includes 6 eruptions and Epoch III (5.5-3.5 ka) includes at least 27 eruptions. The most powerful eruptive events of the last 15 ky are the 11.9-12.1 ka Pomici Principali eruption and the 4.5 ka Agnano Monte Spina eruption. Epoch III was followed by millennia of quiescence culminating in the AD 1538 Monte Nuovo eruption (the last CF eruption), which built a tuff cone (Di Vito et al. 1987. The NYT caldera floor is characterized by a still-active resurgence that started soon after its collapse (Di Vito et al. 1999). Its long deformation history incorporated phases of uplift and subsidence as well as bradyseismic phenomena since Roman time (Di Vito et al. 2016;Isaia et al. 2019). The current activity at Campi Flegrei is characterized by shallow seismicity and fumarolic activity (Chiodini et al. 2021) and a new inflation phase started in 2005(De Martino et al. 2021. Surveillance activities of ground deformation performed by OV, along with other geophysical and geochemical measurements, have been enhanced significantly since the bradyseismic crises of 1970-1972, 1982-1984 and 2005-present. Since 2012, all monitoring activities have further increased due to variations in the monitored parameters (seismic, gaseous, ground deformation, thermal). The permanent seismic network at Campi Flegrei consists of 26 terrestrial and marine stations. The marine infrastructure for multi-parametric investigation consists of 4 geodetic buoys with submarine modules, equipped with geophysical and oceanographic instrumentation. The permanent GPS network for monitoring the ground displacement at Campi Flegrei consists of 25 terrestrial and marine stations. The tiltmeter network for monitoring the ground inclination at Campi Flegrei consists of 10 stations equipped with analogue sensors on ground and analogue and digital sensors in wells. The permanent thermal imaging network at Campi Flegrei consists of 2 stations, acquiring thermal infrared images for the inner flanks of the Solfatara and the fumarolic area of Pisciarelli. Mobile thermal cameras and rigid thermocouples are used to detect eventual timedependent ground temperature variations in discrete points and/or in areas with greater temperature. The geochemical monitoring activities consist of continuous acquisition of the CO 2 flux from the ground, of the fumarole temperature, and of the thermal gradient inside the Solfatara crater and at Pisciarelli (Di Vito and Doronzo 2021). Periodic sampling and analyses of water and gas in selected areas integrate the geochemical measurements, as well as periodic gravimetric and geodetic measurements, and volcanological observations integrate the monitoring activity. The alert level at the time of writing is yellow.

Ischia Island
Ischia Island represents the emerged portion of a wide volcanic structure rising from the seafloor in the Gulf of Naples (e.g. Vezzoli 1988;de Vita et al. 2010;Sbrana et al. 2018). The whole volcanic succession of Ischia covers a time span of more than 150 ky (de Vita et al. 2010). The growth of Ischia continued until 74 ka BP through effusive eruptions that produced lava flows and lava domes and explosive (Plinian) eruptions that produced a sequence of pyroclastic units, separated by paleosols, representing the remnant of an ancient volcanic edifice (Sbrana et al. 2018). Explosive activity resulting in a thick succession of pumice fall deposits separated by paleosols (Pignatiello Formation) occurred around 60 ka BP (Sbrana et al. 2018). The emplacement of the Pignatiello Formation shortly predates the 60-56 ka Monte Epomeo Green Tuff (MEGT) caldera-forming eruptions (Brown et al. 2008). A phase characterized by resurgence of the caldera floor, which started soon after the MEGT eruptions, formed the impressive asymmetric structure of Mt. Epomeo through the discontinuous uplift of a discrete number of differentially displaced blocks (Acocella and Funiciello 1999). A new phase of intense volcanism (28-18 ka) was characterized by the emplacement of Plinian deposits, magmatic to phreatomagmatic activity and effusive eruptions with emplacement of lava domes and lava flows. The last period of activity started about 13-10 ka BP and continued until the last eruption occurred in AD 1302 (Arso eruption) in the eastern sector of Ischia. About 46 eruptions occurred during this last phase of activity, generating lava flows and domes, scoria cones, tuff ring and tuff cones and widespread sheets of ash and pumice lapilli (de Vita et al. 2010). The most violent eruptions of this period are the 5.6 ka "Piano Liguori" eruption and the "Cretaio" eruption that occurred in Roman time (Orsi et al. 1992;Primerano et al. 2021). Volcanism at Ischia has been always accompanied by resurgence and slope instability that generated huge debris avalanches and landslides, intercalated with primary volcanic deposits (de Vita et al. 2006). Currently, resurgence and volcanism are not occurring, with Mt. Epomeo characterized by subsidence, and the activity of Ischia is represented by low seismicity, widespread fumaroles and thermal springs (Selva et al. 2019;Trasatti et al. 2019). The monitoring of Ischia by OV has been improved with the installation of a sophisticated surveillance network after the earthquake that occurred on 21 August 2017 at Casamicciola. The permanent seismic network consists of 8 stations integrated with 3 mobile stations. Such networks allow detection and classification of seismic transients related to earthquakes versus other natural or artificial phenomena. The geodetic measurements are facilitated by a GPS network composed of 6 stations integrated with a station located at Procida Island (De Martino et al. 2021), a tiltmeter network composed of 3 stations complemented by altimetric, gravimetric and periodic InSAR (interferometric synthetic aperture radar) surveys. The volcanological monitoring activities at Ischia are carried out using mobile infrared thermal cameras and rigid thermocouples. Thermal measurements are carried out in nine station points. The geochemical measurements consist of monitoring the chemical composition and temperature of the fumaroles and hydrothermal water. The alert level at the time of writing is green.

The physical and cultural landscape of the Museum of the Osservatorio Vesuviano
Interest in volcanic geoheritage and geotourism has been growing worldwide, as demonstrated by the numerous papers and journal issues dedicated to these topics in recent years (e.g. Németh et al. 2017;Coratza et al. 2018;Planagumà and Martí 2020;Dóniz-Páez 2022;Planagumà-Guàrdia et al. 2022). The volcanic landscape of Somma-Vesuvius has been recognized as a key geoheritage site of remarkable historical, scientific and geologic significance (Németh et al. 2017). The Vesuvius National Park (VNP) was established in 1995 to protect, enhance and disseminate the geo-and bioheritage of the volcano. The presence of Vesuvius stimulated not only scientific progress but also technological and cultural development (Ricciardi 2009). For example, Vesuvius hosted the "Funicolare del Vesuvio" (Funicular of Vesuvius), the only cable railway operating on an active volcano, which carried visitors to the crater. Inaugurated in 1880 and decommissioned in 1944 (Smith 1998), its construction was celebrated by local communities in one of the most famous Neapolitan songs, "Funiculì Funiculà" (Smith 1998).
Vesuvius and its park attract both geotourism and archaeotourism with their proximity to important archaeological sites such as Pompeii and Herculaneum. The VNP covers an area of 8482 hectares, encompassing thirteen municipalities (Fig. 1), and tells the history of the volcano through natural exposures of rock sequences and volcanic landforms. VNP's network of eleven trails, totalling 54 km, allows visitors to enjoy the geodiversity (represented by the variety of rocks, sediments, and minerals; Gray 2013) and geomorphodiversity (revealed in the range of morphological characteristics and landforms; Panizza 2009; Panizza and Piacente 2017) of one of the most studied volcanoes in the world. The geological landmarks visible from VNP's trails include all of Vesuvius' landforms ( Fig. 1) and types of deposits. The principal and most visited trail, named "Gran Cono", leads visitors along the southern rim of Vesuvius crater, offering a panoramic view of the crater's inner walls where outcrops expose products from the time following the 1906 eruption until the 1944 eruption, including the deposits of the 1944 eruption itself (Cole and Scarpati 2010;Di Vito et al. 2011). From there, a spectacular southward view of the densely populated surrounding area makes clear the risks posed by a future eruption of Vesuvius for about 700,000 residents (https:// www. prote zione civile. gov. it/ it/ appro fondi mento/ aggio rname nto-del-piano-nazio nale-di-prote zionecivile-il-vesuv io/). During the ascent to the crater, hikers can look north to see the Valle del Gigante, between Vesuvius cone and Mt. Somma, with the 1944 lava flow and the internal scarp of Mt. Somma in foreground, and they can look northwest to see the smooth morphology of the hill (Umberto Hill), formed by accumulation of lavas erupted at the end of the nineteenth century from the base of the cone. On the southern Vesuvius slope, the "Strada Matrone trail" and "Riserva Tirone trail" pass near the eccentric vents of the 1906 eruption and related lavas. The "Valle dell'Inferno trail" leads to the eastern sector of the "Valle del Gigante", allowing a closer look at the sequence of rocks forming the Mt. Somma scarp, crossed by numerous dykes. The trail named "Il fiume di lava" (the river of lava) lets visitors walk directly on the 1944 lava flow and is conveniently close to the Museum of the OV. The trails named "Il Monte Somma" and "Lungo i Cognoli" run on the Mt. Somma crest, reaching its highest peak (Punta Nasone, 1132 m.a.s.l.) and its secondary peaks (Cognoli) and allowing an exceptional panoramic view of the Vesuvius cone and the Valle del Gigante between them. In addition, superimposition of thick pyroclastic sequences of Plinian and sub-Plinian eruptions (e.g. Santacroce and Sbrana 2003;Di Vito et al. 2009;Sbrana et al. 2020;Doronzo et al. 2022) and deposits of ancient (>22 ka) scoria cones built on eccentric vents (McDonald et al. 2016;Sparice et al. 2017), representing most of the volcanic history of Somma-Vesuvius, are visible in defunct quarries around the volcano (Fig. 1). Some of these are recognized as geosites (Leone 2015) of great interest and value for volcanological and archaeological studies.
Volcanoes and volcanic eruptions have affected the lives of humans many times in history due to the rapid time frame of their action and their constructive and destructive consequences (e.g. De Boer and Sanders 2012;Németh et al. 2017;Cashman and Giordano 2008). The history of Vesuvius is intertwined with that of the communities that lived and still live at its foot or nearby, representing a threat and, at the same time, a catalyst that has allowed communities to thrive thanks to the fertility of volcanic soils and the Mediterranean climate. The effects of Vesuvius' eruptions on human settlements are visible in many archaeological sites (Fig. 13) that add historical and cultural value to the geological and volcanological heritage of the Vesuvius area. Examples of such archaeological heritage are the Roman cities of Pompeii, Herculaneum, Stabiae and Oplontis, along with the Roman villas of Boscoreale, Terzigno and Civita Giuliana, buried by the AD 79 eruption (e.g. Sigurdsson et al. 1985;Cioni et al. 1992;Luongo et al. 2003a, b;Toniolo et al. 2021;Doronzo et al. 2022). More examples are the Roman villa of Emperor Augustus at Somma Vesuviana that survived the effects of the AD 79 eruption and which was later engulfed by the products of the AD 472, AD 512/536 and AD 1631 eruptions (Perrotta et al. 2006); the superimposition of three Roman structures at Pollena Trocchia, sandwiched between the products of the AD 79, AD 472 and AD 512 eruptions (Scarpati et al. 2016); and the effects of the 3.9 ka Avellino Plinian eruption on Bronze Age villages and landscape (e.g. Di Di Lorenzo, 2013;Livadie et al. 2019). Interwoven human and volcanic histories are similarly well documented for Campi Flegrei and Ischia (e.g. de Vita et al. 2013de Vita et al. , 2021Costa et al. 2022).
The Museum of the OV, with its Pompeian-red edifice, stands out in this volcanic landscape that is one of the most iconic in the world (Di Vito et al. 2018). It aims to convey the scientific knowledge and the geo-volcanological importance of the region and make citizens aware of volcanic phenomena, hazards and monitoring activities in this highrisk area. It pursues this commitment not only through traditional and multimedia exhibitions but also through social media and web content, whose importance in modern dissemination and communication has been recently reiterated by Stix and Heiken (2022). In the last few years, the concept of "social volcanology" (e.g. Donovan et al. 2012;Riede 2019;Martin et al. 2020) has become more familiar. Increasingly, volcanologists include social studies in their research, recognizing that the cultural and social fabric of a community shapes that community's response to past and present natural disasters. As a consequence, the interaction between the volcanological community and general public is fundamental to improving the management and mitigation of volcanic and seismic risks. Trust and credibility must be established between scientific institutions, committed to volcano monitoring, and populations that expect quick and accurate information on the state of the volcano and related emergencies. In a densely inhabited area like the Vesuvius territory, this task is not easy, and the role of volcanologists is further complicated by social factors and a low perception of risk by Neapolitans (Carlino 2021). For this reason, the OV collaborates with the VNP to carry out public outreach programs such as field trips on the volcano (e.g. Di Alessio and De Lucia 2017;Cioni et al. 2020).

Conclusions
Throughout the eighteenth century, Italy was one of the essential destinations for travellers of the Grand Tour, a cultural journey undertaken by European young aristocrats and intellectuals through the historic and artistic heritage of the Italian peninsula. Likewise, with the due proportions, we consider the Museum of the OV as an essential stop in what we could define as a modern "Vesuvius Grand Tour".  . The distribution of the 3.9 ka Avellino, AD 79 and AD 472 fall deposits is also reported The Museum of the OV, enclosed in the protected area of the Vesuvius National Park, takes visitors on a cultural and scientific journey through volcanological, geomorphological, mineralogical and all other aspects of the geoheritage of Vesuvius. It delves into the history of the oldest volcano observatory in the world and chronicles the birth of volcano monitoring, from pioneering scientific instruments to modern surveillance activities carried out by INGV-OV on the three Neapolitan active volcanoes, increasing the awareness of people about natural hazards and the concept of volcanic risk. The geoheritage of Vesuvius is also exploited in many archaeological sites around the volcano, among which Pompeii and Herculaneum are the most famous, where volcanology and archaeology form a symbiotic relationship due to volcanic deposits that have engulfed and sealed important archaeological structures for nearly two thousand years preserving them over time.
Acknowledgements INGV -Pianeta Dinamico project financially supported the Grants for two of this paper coauthors. We thank l'Ente Parco Nazionale del Vesuvio for its support in reopening the Museum of the Osservatorio Vesuviano. We are also grateful to the guides that have been guiding countless visitors since 2000. Comments and suggestions provided by Julia Sable and an anonymous reviewer and the editorial work by Christopher Gregg and Marie Edmonds greatly contributed to improve the manuscript.
Funding Open access funding provided by Istituto Nazionale di Geofisica e Vulcanologia within the CRUI-CARE Agreement.
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