The Leaning Tower of Pisa (Italian: torre pendente di Pisa [ˈtorre penˈdɛnte di ˈpiːza, - ˈpiːsa]), or simply the Tower of Pisa (torre di Pisa), is the campanile, or freestanding bell tower, of Pisa Cathedral. It is known for its nearly four-degree lean, the result of an unstable foundation. The tower is one of three structures in Pisa's Cathedral Square (Piazza del Duomo), which includes the cathedral and Pisa Baptistry.