Leaning Tower of Pisa

The Leaning Tower of Pisa (Italian: Torre pendente di 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 is the third oldest structure in Pisa's Piazza del Duomo (Cathedral Square) after the cathedral and the baptistry.

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 tower presently leans to the southwest.

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 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. The tower leans at an angle of 3.97 degrees. This means that the top of the tower is 3.9 metres (12 ft 10 in) from where it would stand if the tower were perfectly vertical.
                                   

Technical information

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 metres (50 ft 9.6 in)
Inner diameter of base: 7.368 metres (24 ft 2.1 in)
Angle of slant: 3.97 degrees[17] or 3.9 m (12 ft 10 in) from the vertical
Weight: 14,700 metric tons (16,200 short tons)
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 or La Giustizia, 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: 296.
A special note on the 5th bell: The name Pasquareccia comes from Easter, because it used to ring on Easter day. However, this bell is older than the bell-chamber itself, and comes from the tower Vergata in Palazzo Pretorio in Pisa, where it was called La Giustizia (The Justice). The bell was tolled to announce capital executions of criminals and traitors, including Count Ugolino in 1289.  A new bell was transferred on the belltower to replace the broken Pasquareccia bell at the end of the 18th century.