The Learning 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. It is situated behind the cathedral and is the third oldest structure in Pisa’s 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 55.86m (183.27ft) from the ground on the lowest side and 56.70 m (186.02ft) 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 leaned at an angle of 5.5 degrees, but after the restoration works between 1990 and 2001 the tower leans at an angle of 3.99 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.
