White marble 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 it is the third structure by time in Pisa's Piazza del Duomo (Cathedral Square). 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 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 meters from where it would stand if the tower were perfectly vertical.