The tower construction was begun in 1173, and after several interruptions for various reasons, was finally completed in 1372. You may assume from this information that none of the workers who began the job were able to see it completed.
The tower was closed to the public on 7 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. 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.
In 1987, the tower was declared as part of the Piazza dei Miracoli UNESCO World Heritage Site along with neighbouring cathedral, baptistery and cemetery.
Certain information and suppositions
The day 5 january 1172 a widow, donna Berta di Bernardo, who lived in the house of the Opera di Santa Maria (ancient name of the cathedral vestry board of Pisa), left in her legacy, that still exist, "sessanta soldi" (sixty penny) to the Opera Campanilis petrarum Sancte Marie, to buy stones and to begin to build the Tower.
The day 9 august 1173 were laid the foundations of the Tower.
Giovanni di Simone was heavily involved in the works of completing the tower, under the direction of Giovanni Pisano, who in that time was master builder of the Opera di Santa Maria Maggiore. Maybe was the same Giovanni Pisano that completed the tower with the bellfry.
Giorgio Vasari, although, indicates Tommaso di Andrea Pisano as the author of the bellfry, between 1360 and 1370.
In 1232 a warehouse were to store the marbles to the tower exist in Pisa.
In the day 27 december 1233 the worker Benenato, son of Gerardo Bottici, undertook to continue the building of the belltower.
In the day 23 february 1260 Guido Speziale, son of Giovanni, is elected worker of Santa Maria Maggiore, and he undertakes to continue the building of the Tower.
In the day 12 april 1264 the master builder Giovanni di Simone with 23 stone masters go to cut marbles in the mountains of Pisa. Those marbles are given to Rainaldo Speziale worker of St. Francesco.
In the day 16 august 1267 Rainaldo Speziale , that was worker of St. Francesco, is recalled as worker of Santa Maria Maggiore (and thus of the belltower). In the same document Giovanni di Simone appears as master builder of the vestry board.
View looking upElevation 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 or 4.5 m from the vertical
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
1st bell: L'assunta, cast in 1654 by Giovanni Pietro Orlandi, weight 3,620 kg (7,981 lb)
2nd bell: Il Crocifisso, cast in 1572 by Vincenzo Possenti, weight 2,462 kg (5,428 lb)
3rd bell: San Ranieri, cast in 1719-1721 by Giovanni Andrea Moreni, weight 1,448 kg (3,192 lb)
4th bell: La Terza (1st small one), cast in 1473, weight 300 kg (661 lb)
5th bell: La Pasquereccia, cast in 1262 by Lotteringo, weight 1,014 kg (2,235 lb)
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)
7th bell: Dal Pozzo, cast in 1606 and again in 2004, weight 652 kg (1,437 lb)
Steps to bell tower: 294
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 and the nearby 14th century bell tower in the town of Bad Frankenhausen (Sunday Telegraph no 2,406- 22nd July 2007)
Answered By: masince1986 - 10/5/2007