The Leaning Tower of Pisa (Italian: Torre pendente di Pisa) or simply the Tower of Pisa (Torre
di Pisa) is the campanile, or
freestanding bell tower, of the cathedral of the Italian city of Pisa,
known worldwide for its unintended tilt to one side. It is situated behind the
Cathedral and is the third oldest structure in Pisa's Cathedral Square (Piazza del Duomo)
after the Cathedral and the Baptistry. The tower's tilt began during
construction, caused by an inadequate foundation on ground too soft on one side
to properly support the structure's weight. The tilt increased in the decades
before the structure was completed, and gradually increased until the structure
was stabilized (and the tilt partially corrected) by efforts in the late 20th
and early 21st centuries.