Leaning Tower of Pisa
Under engineeer Bonanno Pisano, construction on the tower began in 1173 and built using 23,000 blocks of stone; it is almost 56 meters tall with a 293 step spiral staircase and weighs around 14.5 thousand tonnes but built on a foundation 3 meters thick. The style is Romanesque.
Because of the soft clay and sand beneath the foundations it was leaning even before it was complete and work was stopped. Despite the lean, work was resumed in the second half of teh 14th century and it was completed with the lean, however the new construction was angled differently from the old construction to try and compensate.
In 1350 when it was completed it was leaning over by 1.4 meters. Bells were added and slowly the tower began to tilt further until by the late 20th century it was leaning by more than 5 meters.
Restoration and Straightening
In 1838, architect Alessandro Della Gherardesca built a walkway around the tower so that visitors could see its carefully crafted base. Predictably, this only made the lean worse.
In the 1930s Mussolini ordered the foundation to be filled in with concrete, but the concrete sunk into the wet clay and the leaning tower continued its slow fall.
The tower has been closed to visitors at various times as engineers worked to shore up the base, fearful it would eventually topple completely. Many attempts basicaly tried to lower the soil level on the higher side to try and balance the tower out; this was sometimes combined with counterweights to persuade the tower over.
In 1990 it was closed to the public and the bells removed. More earth was removed and the tower straightened straightened by 45 centimetres to the angle it had in 1838.
In 2010 major restoration work was carried out and a lot of work was alos done to try and repair damage caused by tourists (graffiti and handprints), pigeons and general air pollution. There was also a major problem from salt: wind coming in from the sea laden with salt water could not drain away properly from the tower due to its incline.
- The story that Galileo dropped two cannonballs of different weights from the tower to determine their speed of descent is almost certainly apocryphal.
- During the Second World War the American army advancing through Italy ordered that all towers be destroyed to prevent their being used by enemy snipers; fortunately the tower of Pisa was given a reprieve.
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