The Leaning Tower of Pisa is a quintissential Italian image that is recognised all over the world. It is a 'campanile' or bell tower standing independently alongside the cathedral in the Tuscan city of Pisa, which is immediately recognisable by its distictive shape and the angle of lean relative to the Cathedral alongside.
It was constructed of white marble in the 'Piazza Dei Miracoli' (Square of Miracles) also known as 'Piazza Del Duomo (Cathedral Square), a wide, walled area in the centre of Pisa. It was the last of three buildings to be contructed in the square after the Cathedral itself and the Baptistry which stands alongside. It is an important example of medieval art and is widely considered to be one of the finest architectural complexes in the world. The square also houses the 'Camposanto Monumentale' (Monumental Cemetary) and the 'Ospedale Nuovo di Santo Spirito' (New Hospital of the Holy Spirit) and is an important religious area for the Roman Catholic Church as well as being one of the most visited tourist attractions in Italy.
Work started on the construction in 1173, but it took nearly 200 years to complete. The tower began to lean during the early stages of its construction due to inadequate foundations on one side. Once the problem had been recognised, work was halted for some time as Pisa became engaged in successive battles with her neighbours. When work resumed, the subsidence had halted itself and successive builders tried to compensate for the tilt by building one side up higher than the other. This has resulted in the tower being somewhat curved.
Although the engineer Bonanno Pisano definitely worked on the project, it is uncetain whether he was the original architect. It could also have been contemporary architects: Diotisalvi or Guglielmo of Innsbruck.
The tower is 55.86 metres high (183.27 feet) on the lower side and 56.67 metres (185.93 feet) on the higher side. There are 294 steps on one staircase and 296 on the other. The top of the tower remains 3.9 metres (12 ft 10 in) away from the vertical.
In the late 16th century, the tower is said to have been used by Gallileo Gallilei to test his theory on gravity by dropping two cannonballs of different weights from the top of the tower. The story may not be true but it is still often quoted in classrooms.
By the late 20th century the tower was leaning by more than 5 degrees. In 1964 the Italian government requested international help in preventing the likely eventual collapse of the tower. A team of engineers, mathematicians and historians were assembled to develop a plan to protect the tower, at the same time as retaining the degree of tilt that made it such an important tourist attraction for the city of Pisa.
In 1987 the tower was declared part of the 'Piazza del Duomo UNESCO World Heritage Site' along with the neighbouring cathedral, baptistery and cemetery.
After 20 years of studies, the tower was closed to the public in 1990 and work began. The substantial repairs took a further 10 years to complete but finally the lean was stabilised and reduced to less than 4 degrees. The tower was reopened to the public in 2001. Engineers claim to have secured the tower's future for at least 300 years.
Although there are many other contenders for the title of 'World's most leaning building', none of them could ever quite compete with the uniquely iconic qualities of the 'Leaning Tower of Pisa'.
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