The Leaning Tower of Pisa or simply the Tower of Pisa 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 the Cathedral and is the third oldest structure in Pisa’s Cathedral Square (Piazza del Duomo) after the Cathedral and the Baptistery. 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). 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, but the tower now leans at about 3.99 degrees. This means that the top of the tower is displaced horizontally 3.9 metres (12 ft 10 in) from the centre.
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, a well-known 12th-century resident artist of Pisa, famous for his bronze casting, particularly in the Pisa Duomo. Bonanno Pisano left Pisa in 1185 for Monreale, Sicily, only to come back and die in his home town. A piece of cast with 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. However, recent studies seem to indicate Diotisalvi as 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. However, he usually signed his works and there is no signature by him in the bell tower which leads to further speculation.
Construction of the tower occurred in three stages across 199 years. Work on the ground floor of the white marble campanile began on August 14, 1173, during a period of military success and prosperity. This ground floor is a blind arcade articulated by engaged columns with classical Corinthian capitals.
History following construction
Galileo Galilei is said to have dropped two cannonballs of different masses from the tower to demonstrate that their speed of descent was independent of their mass. However, the only primary source for this is a biography, Racconto istorico della vita di Galileo, written by Galileo’s secretary, Vincenzo Viviani, and published in 1717, long after Viviani’s death.
Two German churches have challenged the tower’s status as the world’s most lop-sided building: the 15th-century square Leaning Tower of Suurhusen and the 14th-century bell tower in the town of Bad Frankenhausen. Guinness World Records measured the Pisa and Suurhusen towers, finding the former’s tilt to be 3.97 degrees. In June 2010, Guinness World Records certified the Capital Gate building in Abu Dhabi, UAE as the “World’s Furthest Leaning Man-made Tower”.The Capital Gate tower has an 18-degree slope, almost five times more than the Pisa Tower; however the Capital Gate tower has been deliberately engineered to slant. The Leaning Tower of Wanaka in New Zealand, also deliberately built, leans at 53 degrees to the ground.