The Leaning Tower of Pisa (Italian: Torre pendente di Pisa) or simply the Tower of Pisa (Torre di Pisa) is the campanile, or freestanding bell tower, of the cathedral of the Italian city of Pisa. It is situated behind the Cathedral and is the third oldest structure in Pisa's Cathedral Square (Piazza del Duomo) after the Cathedral and the Baptistry.
The height of thetower is 55.86 m (183.27 ft) from the ground on the low side and 56.70 m (186.02 ft) on the high side. The width of the walls at the base is 4.09 m (13.42 ft) and at the top 2.48 m (8.14 ft). Its weight is estimated at 14,500 metric tons (16,000 short tons). The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north-facing staircase. Prior to restoration work performed between1990 and 2001, the tower leaned at an angle of 5.5 degrees, but the tower now leans at about 3.99 degrees. This means that the top of the tower is displaced horizontally 3.9 meters (12 ft 10 in) from where it would be if the structure were perfectly vertical.
A popular tourist activity is to pose for photographs pretending to "hold up" the leaning tower and preventing it from falling. Theillusion is created through the principle of forced perspective.
Construction of the tower occurred in three stages across 177 years. Work on the ground floor of the white marble campanile began on August 8, 1173, during a period of military success and prosperity. This ground floor is a blind arcade articulated by engaged columns with classical Corinthian capitals.
The tower began tosink after construction had progressed to the second floor in 1178. This was due to a mere three-meter foundation, set in weak, unstable subsoil, a design that was flawed from the beginning. Construction was subsequently halted for almost a century, because the Republic of Pisa was almost continually engaged in battles with Genoa, Lucca and Florence. This allowed time for the underlying soil tosettle. Otherwise, the tower would almost certainly have toppled. In 1198 clocks were temporarily installed on the third floor of the unfinished construction.
In 1272 construction resumed under Giovanni di Simone, architect of the Camposanto. In an effort to compensate for the tilt, the engineers built upper floors with one side taller than the other. Because of this, the tower is actuallycurved. Construction was halted again in 1284, when the Pisans were defeated by the Genoans in the Battle of Meloria.
The seventh floor was completed in 1319. It was built by Tommaso di Andrea Pisano, who succeeded in harmonizing the Gothic elements of the bell-chamber with the Romanesque style of the tower. There are seven bells, one for each note of the musical major scale. The largest one wasinstalled in 1655. The bell-chamber was finally added in 1372.
After a phase (1990–2001) of structural strengthening, the tower is currently undergoing gradual surface restoration, in order to repair visual damage, mostly corrosion and blackening. These are particularly pronounced due to the tower's age and its exposure to wind and rain.
On January 5, 1172, Donna Berta di Bernardo,a widow and resident of the house of dell'Opera di Santa Maria, bequeathed sixty soldi to the Opera Campanilis petrarum Sancte Marie. The sum was then used toward the purchase of a few stones which still form the base of the bell tower.
On August 9, 1173, the foundations of the Tower were laid.
Nearly four centuries later Giorgio Vasari wrote : "Guglielmo, according to what is being said, in[this] year 1174 with Bonanno as sculptor, laid the foundations of the belltower of the cathedral in Pisa."
Another possible builder is Gerardo di Gerardo. His name appears as a witness to the above legacy of Berta di Bernardo as "Master Gerardo", and as a worker whose name was Gerardo.
A more probable builder is Diotisalvi, because of the construction period and the structure's affinities with...