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The 'Leaning Tower of Pisa' () or simply 'The Tower of Pisa' ('''La 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 it is the third structure in Pisa's Campo dei Miracoli (''field of Miracles'').
Although intended to stand vertically, the tower began leaning to the southeast soon after the onset of construction in 1173 due to a poorly laid foundation and loose substrate that has allowed the foundation to shift direction.
The height of the tower is 55.86 m (183.27 ft) from the ground on the lowest side and 56.70 m (186.02 ft) on the highest 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 tonnes. The tower has 294 steps. The tower leans at an angle of 5.5 degrees^[1]. This means that the top of the tower is 4.5 meters from where it would stand if the tower was perfectly vertical. ^[2]

Contents

Construction

History

Technical information

Notes

References

See also

External links

Construction

The Tower of Pisa was a work of art, performed in three stages over a period of about 174 years. Construction of the first floor of the white marble campanile began on August 9, 1173, a period of military success and prosperity. This first floor is surrounded by pillars with classical capitals, leaning against blind arches.
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 ^[3], 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. His sarcophagus was discovered at the foot of the tower in 1820.
The tower began to sink after construction progressed to the third floor in 1178. This was due to a mere three-meter foundation, set in weak, unstable subsoil. This means the design was flawed from the beginning. Construction was subsequently halted for almost a century, because the Pisans were almost continually engaged in battles with Genoa, Lucca and Florence. This allowed time for the underlying soil to settle. Otherwise, the tower would almost certainly have toppled. In 1198, clocks were temporarily installed on 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 higher floors with one side taller than the other. This made the tower begin to lean in the other direction. Because of this, the tower is actually curved.^[4] Construction was halted again in 1284, when the Pisans were defeated by the Genoans in the Battle of Meloria.
The bell-chamber was not finally added until 1372. 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 scale. The largest one was installed in 1655.
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 strong due to the tower's age and to its particular conditions with respect to wind and rain.^[5]

History

Galileo Galilei is said to have dropped two cannon balls of different masses from the tower to demonstrate that their descending speed was independent of their mass. This is considered an apocryphal tale, and the only source for it comes from Galileo's secretary.
Benito Mussolini ordered that the tower be returned to a vertical position, so concrete was poured into its foundation. However, the result was that the tower actually sank further into the soil.^[6]
During World War II, the Allies discovered that the Nazis were using it as an observation post. A humble U.S. Army sergeant was briefly entrusted with the fate of the tower. His decision not to call in an artillery strike saved the edifice.⁶
On February 27, 1964, the government of Italy requested aid in preventing the tower from toppling. It was, however, considered important to retain the current tilt, due to the vital role that this element played in promoting the tourism industry of Pisa.^[7] A multinational task force of engineers, mathematicians and historians was assigned and met on the Azores islands to discuss stabilization methods. After over two decades of work on the subject, the tower was closed to the public in January 1990. While the tower was closed, the bells were removed to relieve some weight, and cables were cinched around the third level and anchored several hundred meters away. Apartments and houses in the path of the tower were vacated for safety. After a decade of corrective reconstruction and stabilization efforts, the tower was reopened to the public on December 15, 2001. It was found that the lean was increasing due to the stonework expanding and contracting each day due to the heat of sunlight. This was working in combination with the softer foundations on the lower side. Many methods were proposed to stabilize the tower, including the addition of 800 metric tons of lead counterweights to the raised end of the base.^[8] The final solution to prevent the collapse of the tower was to slightly straighten the tower to a safer angle, by removing 38 m³ of soil from underneath the raised end. Through this, the tower was straightened by 18 inches (45 centimeters), returning to the exact position that it was in 1838. The tower has been declared stable for at least another 300 years.⁸
In 1987, the tower was declared as part of the Campo dei Miracoli UNESCO World Heritage Site along with neighbouring cathedral, baptistery and cemetery.

Technical information

★ Elevation of Piazza dei Miracoli: about 2 metres (6 feet, DMS)

★ Height: 55.863 metres (183 ft 3 in), 8 stories

★ Outer diameter of base: 15.484 m

★ Inner diameter of base: 7.368 m

★ Angle of slant: 5.5 degrees^[9] or 4.5 m from the vertical^[10]

★ Weight: 14,700 tonnes

★ Thickness of walls at the base: 8 ft (2.4 m)

★ Total number of bells: 7, tuned to musical scale, clockwise

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★ 1st bell: L'assunta, cast in 1654 by Giovanni Pietro Orlandi, weight 3,620 kg (7,981 lb)

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★ 2nd bell: il Crocifisso, cast in 1572 by Vincenzo Possenti, weight 2,462 kg (5,428 lb)

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★ 3rd bell: San Ranieri, cast in 1719-1721 by Giovanni Andrea Moreni, weight 1,448 kg (3,192 lb)

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★ 4th bell: La Terza (1st small one), cast in 1473, weight 300 kg (661 lb)

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★ 5th bell: La Pasquereccia, cast in 1262 by Lotteringo, weight 1,014 kg (2,235 lb)

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★ 6th bell: il Vespruccio (2nd small one), cast in the 14th century and again in 1501 by Nicola di Jacopo, weight 1,000 kg (2,205 lb)

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★ 7th bell: Del Pozzetto, cast in 1606, weight 652 kg (1,437 lb)

★ Steps to bell tower: 294^[2]

Notes

1. Recently two German churches have challenged the tower's status as the world's most lop-sided building: the 13th century square tower at Suurhusen [1] and the nearby 14th century bell tower in the town of Bad Frankenhausen (Sunday Telegraph no 2,406- 22nd July 2007)

2. The Children's Visual World Atlas, , Andrew, Davies, The Fog Press, , ISBN 1-740893-17-4
3. Controversy about the identity of the architect
4. Do Fish Drink Water?, , Bill, McLain, William Morrow and Company, Inc, ,
5. Restoration work is mentioned inside the official website of the square [2]
6. Shrady, Nicholas. (2003). ''Tilt: a skewed history of the Tower of Pisa''. New York: Simon & Schuster.
7.
8.
9. "BBC On This Day", BBCi
10. Fall of the Leaning Tower
11. The Children's Visual World Atlas, , Andrew, Davies, The Fog Press, , ISBN 1-740893-17-4

References

★ Tilt: a skewed history of the Tower of Pisa, , Nicholas, Shrady, Simon & Schuster, , ISBN 0-7432-2926-6

See also

★ List of leaning towers

★ Round tower, for other types of round towers.

★ Leaning Tower of Niles, a replica of the Tower of Pisa

★ Torre delle Milizie, a tilting medieval tower in Rome

★ Machang - another leaning tower

★ The Greyfriars Tower - the remains of a Franciscan monestry in King's Lynn. It is also leaning and is consequently nicknamed 'The Leaning Tower of Lynn' in reference to the Leaning Tower of Pisa.

External links

★ Satellite view of Leaning Tower of Pisa

★ Holiday Local Map Guide

★ The Leaning Tower of Pisa Virtual reality movies

★ The Official Site In both English and Italian

★ How the process of inclination was stopped

★ The Leaning Tower of Pisa - Map

★ Pictures of Leaning structures

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