Ciechocinek Spa — the Biggest Health Resort in the Polish Lowlands in Terms of Geotourism

Ciechocinek is known for its unique saline graduation towers and salt works. The crucial date in Ciechocinek’s history was 1836, when four treatment copper bath tubs were installed in the local inn. This gave rise to the beginning of the Health Springs Enterprise, which was the origin of the Health Resort. The graduation towers of Ciechocinek are particular and they are the biggest wooden constructions which serve to vaporize brine’s water from the spring no. 11. The graduation towers were built in the shape of a horseshoe. Two first graduation towers were built in the years between 1824 and 1828 and the third in 1859. The height of towers is about 15.8 m and the total length of all of them is more than 1741.5 m. They constitute a unique monument of the nineteenth-century technology, one of few in Europe. In the graduation towers the concentration of salt brine takes place as a part of the salt production process. A characteristic feature of this process is the production of a natural aerosol with healing properties. Within the graduation towers there is a specific microclimate, a natural and curative inhaler. The technology of salt production, which is based on heating concentrated salt brine, has not changed in 190 years — it consists in heating concentrated brine. Thermal brines of the Na–Cl type and J type from borehole no. 14 (Terma 14) and borehole no. 16 (Terma 16) are used for Ciechocinek Spa mineral water supply. These boreholes are screened in the Dogger and Lias sandstones. The water in Terma 14 has mineralization (total dissolved solids (TDS)) of 43.5 g/L and the temperature on the borehole outflow is 28 °C. The water from Terma 16 has mineralization (TDS) of 53.4 g/L. It is thermal water and its temperature on the borehole outflow is 32 °C. The therapeutic thermal water in the Ciechocinek boreholes occurs at considerable depth and its resources are very slowly renewable. The therapeutic qualities of Ciechocinek springs are strongly recommended for curing cardiovascular, respiratory, orthopedic, traumatic, rheumatic, nervous system, and women’s diseases. The Ciechocinek Spa is a producer of well-known products of perfect quality: “Krystynka” mineral water, flavored water, table salt, medicinal lye, and mud.


Introduction
In the area of Poland there are 44 municipalities which have been granted the status of health resorts. Their operation is based primarily on mineral and thermal waters. According to the Polish geological and mining law, curative waters are defined as those underground waters which are uncontaminated in terms of their chemical and microbiological status, which are characterized by natural variability of their physical and chemical properties, and which contain 1 g/L of dissolved substances (Ciężkowski et al. 2010). Low mineralized water can also be regarded as curative as long as it contains at least one specific component and/or is characterized by temperature exceeding 20 °C. Brines include mineralized waters reaching the concentration of at least 35 g/L, whose main components are the following ions: chloride, sodium, and calcium. The greatest resources of such waters, both mineral, thermal, and brines, have been identified in the area of the Polish Lowlands, and more specifically in a small town called Ciechocinek (Krawiec 1999).
The history of Ciechocinek is inextricably connected with the village of Słońsk, where salt was refined from brines already in the thirteenth century. In 1824 the construction of the salt works and graduation towers started in Ciechocinek, where they have been in operation ever since and nowadays belong to the most valuable tourist sites.
Ciechocinek is a well-known health resort which is assumed to have started its activity in 1836, when four copper healing baths were installed in a local inn. Approximately 120 people took advantage of the saline baths at the time (Raczyński 1935). This event gave rise to the establishment of the Spa Facility, which turned out to be a nucleus of the modern health resort. Since that time, the town has gained considerable recognition as a health resort. Subsequently the baths were constructed and the number of healing baths as well as resort patients have increased considerably.
In Ciechocinek, the following diseases are treated: musculoskeletal, rheumatic, orthopedic, and traumatic; gynecological; respiratory; and those connected with the nervous and cardiovascular systems. For these purposes, in the course of treatment, many different procedures are performed such as saline baths, iodine and bromine baths, sulfur baths, and partial or complete mud wraps, inhalations, irrigations, climatotherapy, or massages (Ponikowska 2007). For these procedures, thermal brines of the Cl-Na and J types are used from the borehole nos. 14 and 16, whose total salt concentrations amount to 43-54 g/dm 3 , and whose temperatures reach 26-32 °C (Krawiec 1999).
In the northern part of the resort, the Spa Park, established between 1875 and 1876, is located. The park abounds in exuberant and diverse vegetation and rich floral decorations which form the famous flower-carpets. Every year Ciechocinek is visited by numerous resort patients as well as tourists. For instance, in 1980 the health resort was visited by 52,000 patients; in 1987, their number rose to approximately 85,000, whereas in recent years, in excess of 120,000 patients and tourists have visited this town (www. stat. gov. pl).

Study Area
Ciechocinek is situated in the Vistula River Valley, on the western bank of the river, within the distance of 2 km from the mainstream of the river (Fig. 1). The town is located on low alluvial terraces. This area belongs to the south-eastern part of the Toruń Basin, which is locally known as the Lowland or the Ciechocinek Basin. The plain area includes also the lowest alluvial terraces of the Vistula. In order to prevent the area from being flooded, a 6.5-km flood embankment was erected in Ciechocinek in 1872. The subsequent embankments were built from the direction of Wołuszewo, each measuring 0.55 km, and from Warzelniana Street to the graduation tower, an inner antiflood barrier was constructed (Raczyński 1935).

Geological Structure and Hydrological Conditions
The area of Ciechocinek belongs to the Kuyavian part of the Central Polish anticlinorium, within which the Mesozoic layers are uplifted and undulating. The thickness of the Pleistocene and Holocene sediments in the study area is variable and ranges from several meters in the vicinity of the Ciechocinek town center to several dozen meters towards the north and north-west of the resort. The Holocene sediments include river and dune sands, sands and diluvial clays, and peats or silts. The Pleistocene formations include mainly river sands from the alluvial terraces of the Vistula as well as fluvioglacial sands and glacial tills. The Miocene sediments have thickness reaching several meters (Fig. 2) and they do not constitute a solid layer -they do not occur in the center of Ciechocinek (Krawiec 2005). These layers are formed of loams with lignite and sandy inserts.
The Jurassic sediments in the vicinity of Ciechocinek have a thickness of approximately 1300 m. These are mostly formations of Malm, Middle Jurassic period, and Lias. The Malm rocks include mainly oolitic limestones, marlstones, clay stones, and clay limestones with dolomite inserts. The Middle Jurassic period is represented by multi-grained sandstones as well as shales. Inserts of limestones, loams, and clay stones can also be found. The Lias sediments are as follows: sandstones with the interbedding of shales, mudstone schist, and clay stones (Samsonowicz 1954). The Triassic sediments belong to the oldest sediments drilled in the vicinity of Ciechocinek. They have been identified at the depth of 1295-1365 m in the borehole nos. 18, 16, and 14. These are shales, dolomite limestones, and siltstones and clay stones (Dowgiałło et al. 1968).
The hydrogeological conditions in the study area are inextricably connected with the geological structure of the region, in which the Vistula River Valley constitutes the local drainage base for the waters flowing in from moraine elevations. In this area the Quaternary and Jurassic aquifers can be distinguished.
The Quaternary aquifer is linked to a series of sandy and gravel alluvia with a free water-bearing table, which can be found at the depth from 1 to 5 m. This water-bearing level is recharged by direct infiltration of precipitation as well as by a lateral groundwater inflow from the Kuyavian Upland. In the zones of direct contact between the Quaternary and Jurassic aquifers, there is a possibility of the mixing of waters from both aquifers (Witkowska et al. 2002).
The waters of the Jurassic aquifer are under considerable pressure and can recharge the Quaternary water-bearing level by means of ascension (Krawiec 1999(Krawiec , 2005. Research has shown that in a substantial part of the study area, the content of Cl − ions in the waters of the Quaternary aquifer exceeds 250 mg/dm 3 , whereas in the central part of Ciechocinek reaches even a few thousand mg/dm 3 . The Jurassic aquifer occurs in series of cracked sandstones and limestones. These are chloride and sodium brines, iodine brines, and weakly mineralized chloride and sodium waters. A characteristic feature of the Ciechocinek brines is higher concentrations of bromine and iodine. They contain also insignificant amounts of SO 4 2− and H 2 S. Depending on the location and depth of the intake, the mineralization of water from the Jurassic formations ranges from 3 to 71 g/dm 3 . During the process of drilling the borehole no. 18 in the Triassic formations at the depth of over 1521 m, the brine of the Cl-Na type was identified, the mineralization of which exceeded 80 g/dm 3 (Dowgiałło et al. 1968). Due to the low efficiency of the Triassic aquifer, the borehole has been closed.
For treatment procedures, only two thermal brines from the intake no. 14 and no. 16 are applied, for which water is extracted by means of several meters self-outflows. The thermal well no. 14 was constructed between 1929 and 1932. Initially, its depth did not exceed 1305 m; however, the failure of the well in 1938 caused the reduction of the borehole to the depth of 757 m. The thermal well no. 16 was drilled to the depth of 1378 m between 1949 and 1952  (Samsonowicz 1954). In Ciechocinek there is also the third borehole with thermal water. This is the thermal intake no. 18, whose depth reaches 1450 m (the initial depth was even 1825 m). However, this intake has not been in operation for the last 40 years. The intake no. 11 (Mushroom) was completed between 1909 and 1911 to the depth of 414.5 m (currently only 405 m) and it provides brines, the mineralization of which amounts to 46.9 g/dm 3 to the graduation towers. The intake no. 19a, the depth of which does not exceed 36 m, was drilled in 1978. This borehole takes in water from the late Jurassic water-bearing levels. Water from this intake is bottled and sold under the label of "Krystynka." For mineralized waters from the area of Ciechocinek, it has been observed that along with the rise of depth, there is a gradual growth of mineralization. The analysis of the results of the chemical composition of mineral water from Ciechocinek between 1970 and 2009 has shown a considerable stability of particular components of the brine from the intake no. 14. Over the past 40 years, the constant amount of Cl − ions, which reaches approximately 26.0 g/dm 3 , has been observed. In the case of the brine from the intake no. 11, a gradual decline in the mineralization values has been observed. For example, the concentration of chlorides has fallen from 31 g/dm 3 in 1974 to approximately 27 g/dm 3 nowadays. In the case of the brine from the intake no. 16, the content of the Cl − ions was stable and reached the level of approximately 39 g/dm 3 until 1990. Over the last several years a decline in the concentration of Cl − ions in the brine from the intake no. 16 to the level of 32-34 g/dm 3 has been observed (Krawiec 2005(Krawiec , 2009. Similarly, in the case of the intake no. 19a (Krystynka), from which water of the Malm formations is extracted, the content level of chlorides has fallen from 1.76 g/dm 3 in 1978 to 1.52 g/dm 3 nowadays (Table 1).
For treatment procedures, the chloride and sodium thermal brine and the iodine thermal brine from the intake no. 14 and no. 16 are applied. Their mineralization levels amount to 43.5 g/dm 3 and 53.4 g/dm 3 , respectively (Table 1). Currently, from the intake no. 14 approximately 92 m 3 /d of water with the temperature between 26 and 28 °C is extracted, whereas from the intake no. 16 approximately 35 m 3 /d of brine with the temperature between 28 and 32 °C is extracted. The curative water of the Cl-Na and J types with the concentration level of 4.69% (mineralization 46.9 g/dm 3 ) is extracted from the well no. 11 and is pumped into the "Mushroom" fountain as well as into the graduation towers, from which it makes its way to the salt works. From the well no. 19a only approximately 5 m 3 /d of chloride and sodium water with the mineralization level of 3.2 g/dm 3 is extracted. This type of water is subsequently bottled in the mineral water bottling plant.
The thermal healing waters from the Ciechocinek Health Resort occur at a significant depth and their resources are poorly renewable. These waters are located in the zone of rather difficult exchange and on the basis of the results of chemical and isotopic analyses, it can be concluded that these are probably paleo-infiltration waters from the Quaternary period (Krawiec 2005). In these waters one can also identify small amounts of other types of waters, for instance, admixtures of seawater or residual relic water.
The greatest tourist attraction in Ciechocinek are the graduation towers, the constructions designed by Jakub Graff -a professor from the Mining Academy in Kielce. The graduation towers are arranged in the shape of a horseshoe (Fig. 4).
The construction of the graduation tower no. 1 and no. 2 took place between 1824 and 1828, and the third one was built in 1859. The foundation of the graduation towers is formed by 7000 oak piles, stuck in the ground, on which the construction made of spruce-pine filled with blackthorn is placed and the brine flows here. The height of the graduation towers is 15.8 m, whereas their combined length reaches 1741.5 m (Iwanowska-Jeske 1983). The brine is pumped into the graduation tower from the source no. 11 (Mushroom) and then it is pushed up into a set of wooden troughs, from which it seeps through the walls of the graduation towers filled with blackthorn bush twigs by gravitation. Owing to the action of the wind and sun rays, the brine evaporates and its concentration increases, which creates the so-called "graduation tower spray" around the graduation towers, which is rich in iodine and which, in turn, creates a natural curative inhalation zone. The concentrated brine comes from the graduation towers to the salt pans (Fig. 5), which have been in operation for the last 190 years.
In 1824 the construction of the salt works was started in Ciechocinek and towards the end of 1830 the first trial run of the  (Raczyński 1935). After the construction of the graduation towers and the completion of the salt works in 1836, four copper healing bath tubs were installed in a local inn. These were the beginnings of the Spa Facility due to which Ciechocinek swiftly became a popular health resort. The graduation towers together with the salt works constitute a unique set of historical monuments which are unparalleled in the world and are completely available to tourists for sightseeing. The part of the salt works which is no longer in operation for salt production has been converted to a museum which displays exhibits connected not only to salt production, but also to the business activity of the Ciechocinek health resort. Particular attention should be paid to the renovated equipment used for therapeutic physical training which used to belong to Wilhelm Zander (Swedish doctor) (Fig. 6).
On the basis of saline deposits from the intake no. 11 (Mushroom), Ciechocinek Health produces a variety of treatment products which are applied in medical prophylaxis and as household products. These products include liquor, medical sludge, and evaporated salt.
The Ciechocinek evaporated salt is produced in the salt works and apart from sodium chloride, it contains considerable amounts of calcium, magnesium, sulfates, and higher concentration of iodine (5.24 mg/kg). This type of salt can be used prophylactically in those regions of Poland where deficiencies of iodine in water, soil, and air have been found. The healing liquor and sludge are by-products of salt evaporation process. The liquor is a 31.6% water solution of mineral salts (Ponikowska 2007). It is applied for healing baths after at least tenfold dilution. In comparison with the Ciechocinek evaporated salt, the healing sludge is characterized by high concentration of calcium, magnesium, bromine, and iodine ions. It is used only for bathing and it is applied in the form of a solution containing 100 L of water, 3 kg of sludge, and 1 kg of liquor (Ponikowska 2007).
Therapeutic indications for liquor and healing sludge baths are similar. The 10-20% sludge solutions are used for compresses in therapies of rheumatic diseases and post-traumatic healing of musculoskeletal system. Moreover, liquor can be applied in rheumatoid treatment, nervous system disorders (neuralgic pains and chronic inflammations of nerves), arterial hypertension, peripheral arterial disease, and certain allergic skin problems. In the case of inhalations, liquor can be used for treating chronic catarrh of upper respiratory passages, emphysema, bronchial asthma, bronchitis, and occupational respiratory system hazards (Ponikowska 2007).
The Ciechocinek Spa Company is also the producer of the bottled mineral water called Krystynka. Its production was launched originally in 1902. In the water bottling plant the 0.32% Cl-Na mineral water extracted from the intake no. 19a is produced (Krawiec 2005). It is a natural highly mineralized water of a slightly salty taste. It can be recommended to people working in onerous thermal conditions (several years ago huge quantities of Krystynka were sent to steel mills, coal mines, or power stations) or sports athletes so that they could replenish important electrolytes (Ponikowska 2007).
Very close to the graduation towers, there is a "Ciechocinek" halophyte reserve (Fig. 7). This area of 1.88 ha has been legally protected since 1963 to preserve rare inland halophytic flora (Wilkon-Michalska 1962, 1970. It has been The town can boast of a number of architectural monuments such as the complex of baths (Bath I from 1845 to 1849, Bath II from 1910 to 1912 in the romanesque style, Bath III from 1898 to 1900, and Bath IV from 1900 to 1906) (Raczyński 1935;Iwanowska-Jeske 1983). In Ciechocinek tourists can also find the historical Summer Theatre, the railway station complex (the old station dating back from 1870 is of timberframe construction, while the new one was erected in 1901), St. Peter and St. Paul's neo-Gothic church built between 1877 and 1884, an Orthodox Church erected in 1894, and the water tower, which goes back to the first half of the twentieth century.

Conclusions
• The curative thermal waters from the Ciechocinek health resort occur at a considerable depth and their resources are poorly renewable. These waters occur in a difficult transition zone. For balneological procedures, thermal brines of the Na-Cl type, the mineralization levels of 43 ÷ 54 g/dm 3 , and temperature reaching 26 ÷ 32 °C are applied. They are extracted from the borehole no. 14 (Terma 14) and no. 16 (Terma 16), which take in water from the early and middle Jurassic aquifers. • The Ciechocinek health resort treats mainly rheumatic diseases and musculoskeletal system injuries, cardiovascular disorders, and respiratory illnesses, both in adults and children alike.
• The unique graduation towers and the salt works, which are available to tourists, belong to the unparalleled monuments of human technology from the nineteenth century. The part of the salt works which is no longer in operation for salt production has been converted to a museum which displays exhibits connected not only with salt production, but also with the business activity of the Ciechocinek Spa Company, among which particular attention should be paid to the renovated equipment used for therapeutic physical training which used to belong to Wilhelm Zander. • Apart from the graduation towers and the salt works, the Spa Park, which occupies the area of 19 ha, together with the Mineral Water Pump-house of the post and beam constructional design from 1881, the Concert Shell in the Zakopane style from 1909, and the Hanzel and Gretel Fountain from 1926 are well worth visiting (Iwanowska-Jeske, 1983). In the part of the town where the health resort is situated, there are numerous squares and flowerbeds with impressive floral compositions such as famous flower-carpets as well as the Mushroom fountain located in the area of the intake no. 11. Data Availability https:// geojo urnals. pgi. gov. pl/ pg/ artic le/ view/ 15728.

Conflict of Interest
The authors declare no competing interests.
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