Pisa tower

The Leaning Tower of Pisa (Italian: Torre pendente di Pisa) or simply the Tower of Pisa (Torre di Pisa [ˈtorre di ˈpiːza]) is the campanile, or freestanding bell tower, of the cathedral of the Italian city of Pisa, known worldwide for its unintended tilt.

It is situated behind Pisa's cathedral and is the third oldest structure in the city's Cathedral Square (Piazza del Duomo), after the cathedral and the Pisa Baptistry. The tower's tilt began during construction, caused by an inadequate foundation on ground too soft on one side to properly support the structure's weight. The tilt increased in the decades before the structure was completed and gradually increased until the structure was stabilized (and the tilt partially corrected) by efforts in the late 20th and early 21st centuries.

The height of the tower is 55.86 metres (183.27 feet) from the ground on the low side and 56.67 metres (185.93 feet) on the high side. The width of the walls at the base is 2.44 m (8 ft 0.06 in). Its weight is estimated at 14,500 metric tons (16,000 short tons).[1] The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north-facing staircase. Prior to restoration work performed between 1990 and 2001, the tower leaned at an angle of 5.5 degrees,[2][3][4] but the tower now leans at about 3.99 degrees.[5] This means the top of the tower is displaced horizontally 3.9 metres (12 ft 10 in) from the centre.[6]
There has been controversy about the real identity of the architect of the Leaning Tower of Pisa. For many years, the design was attributed to Guglielmo and Bonanno Pisano,[7] a well-known 12th-century resident artist of Pisa, famous for his bronze casting, particularly in the Pisa Duomo. Pisano left Pisa in 1185 for Monreale, Sicily, only to come back and die in his home town. A piece of cast bearing his name was discovered at the foot of the tower in 1820, but this may be related to the bronze door in the façade of the cathedral that was destroyed in 1595. A 2001 study[8] seems to indicate Diotisalvi was the original architect, due to the time of construction and affinity with other Diotisalvi works, notably the bell tower of San Nicola and the Baptistery, both in Pisa.