The Leaning Tower of Pisa (Italian: Torre pendente di Pisa) or simply the Tower of Pisa is a freestanding bell tower of the cathedral of the Italian city of Pisa, known worldwide for its unintended tilt. The tower's tilt began during construction between 1173 and 1372, caused by an inadequate foundation on ground too soft on one side to properly support the structure's weight. The tower now leans at about 3.99 degrees after restoration work performed between 1990 and 2001. The height of the tower is 55.67m (185.93ft) from the ground on the low side and 56.67 (185.93ft) on the high side. The width of the walls at the base is 2.44m (8ft 0.06 in).