Leaning Instability: The Tower of Pisa, Italy

Abstract

The Tuscan town of Pisa became a powerful Mediterranean republic and a flourishing commercial center in the 11th to 13th centuries. After a decisive victory in a sea battle at Palermo against the Saracens in 1063, its colonies included Sardinia, Corsica, Elba, parts of Southern Spain, and Carthage. It reached the peak of its power in the 12th century as a naval base for the first Crusade to the Holy Land, but in the 13th century, a number of bad political choices and military defeats lead to its demise and domination by Genoa and Florence. Though being the birthplace of Galileo Galilei (1564 – 1642), the town is probably best known for its Romanesque Leaning Tower (Fig. 3.1a). It was built as a bell tower of the cathedral complex on Piazza dei Miracoli (the Square of Miracles, Fig. 3.1b). The construction of the complex was initially funded from the treasure found on six large, heavily loaded ships captured in 1063 from the Saracens, and was meant to demonstrate the power of the Church and the Republic. Excessive inclination, however, turned the Leaning Tower very early into a curiosity and a tourist attraction. In 1990, however, due to the alarming tilt of almost 5.5 degrees and recent collapse of the civic tower in Pavia, which caused four fatalities, it was closed to the public. An elaborate and expensive stabilization campaign followed, which returned the Leaning Tower to its inclination of 1844. In December 2001, it was again opened to the public.