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The History   Pisa Tower
Here, however, the Tower assumes an unusual value through its dislocation from the other monuments in the area of Piazza dei Miracoli. The building is in fact sited in one of the most visible points of the Piazza, in correspondence with the junction between the latter and via Santa Maria, one of the antique thoroughfares of the city. Originally, a road which followed the course of via Emilia passed to the left of the Tower.
 La Torre di Pisa
This is reflected in the sculptural decoration of the ground floor of the Tower, in which motifs and elements to be found in the architecture of the Cathedral are used, while the circular form of the Tower would seem to relate to the curves of the Cathedral's two apses. The Tower, with its great height, was a visual fulcrum, visible from all areas of the Piazza, and, probably, from the river Arno. In this way the Tower assumed the function of both connection between the city and the piazza, sited in a decentralised area of the urban nucleus, and beacon: a reference point and look-out and, ultimately, an authoritative symbol of the civic and religious pride of the Pisan community. The problem of the inclination
The problem of the inclination of the Tower is the aspect which, over the centuries, has most fascinated and aroused the curiosity of visitors, art enthusiasts and scholars, rendering the building world famous.
This is also due to the fact that, to this day, the reasons behind the inclination of the Tower are in many ways mysteries. Experts have debated at length, in particular in the XIX century, over whether or not the inclination came about as a result of problems of statics which emerged during the construction of the Tower: in other words, whether the inclination was the result of an unforeseen and inevitable progressive subsidence of the ground, or whether it constituted an effect consciously desired by the architect.
In the course of the XX century the increasingly accurate measurements of the Tower, alongside the investigations conducted with various instruments into the subsoil and archival and historical research have allowed for the emergence of some certainties (though these too cannot be considered definitive). For example, it now seems certain that the Tower was originally conceived as a straight building, but that it began to give way during the early phases of construction. This was caused by the particular morphological characteristics of the ground underneath, composed of various strata formed of deposits and clayish material, interlayered, at about a metre of depth, by strata of subterranean waters. This conclusion has been reached by observing the composition of the ground and the corrections made to each floor of the Tower. Given the sporadic documentary evidence which we possess, it would appear certain that the oscillation of the building over the centuries was minimal, it having probably settled into a certain equilibrium with the subsoil. This is confirmed by the accurate survey undertaken in 1817 by two English scholars, Cresy and Taylor.
A few years later, in 1838, events caused a brusque acceleration of the oscillating movement of the Tower, leading to the need for resolute conservation operations. In this date, in fact, on the basis of exigencies of historical and aesthetic nature, it was decided to free the base of the Tower from the blanket of earth with which it had been covered for centuries. This operation, which led the Tower to lose the equilibrium which it had acquired, also included the dismantling of the buildings and structures nearby and, above all, the drying of the stagnant waters which perennially encircled the entrance. Subsequent measurements recorded an increase in the inclination of about 20 centimetres, while in the 267 years between the surveys of Giorgio Vasari in 1550 and Cresy and Taylor in 1817, the inclination had increased by a mere 5 centimetres.
After the works of 1838 the acceleration of the inclination continued for some years, after which it decreased to about a millimetre per year. Over the XX century, increases in knowledge and improvements in technical instruments, together with the involvement of conservation and government authorities, have promoted studies, research and even conservation interventions. Since 1988 the Tower has been closed to the public and a committee of experts is working to evaluate every danger likely to worsen the inclination of the Tower and to develop definitive measures to block, and hopefully to invert, the inexorable inclination of the monument towards the ground. |
