The Leaning 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, known worldwide for its nearly four-degree lean, the result of an unstable foundation. The tower is situated behind the Pisa Cathedral and is the third-oldest structure in the city's Cathedral Square (Piazza del Duomo), after the cathedral and the Pisa Baptistry.

The tower was closed to the public on 7 January 1990, after more than two decades of stabilisation studies and spurred by the abrupt collapse of the Civic Tower of Pavia in 1989. The bells were removed to relieve some weight and cables were cinched around the third level and anchored several hundred meters away. Apartments and houses in the path of a potential fall of the tower were vacated for safety.

The selected method for preventing the collapse of the tower was to slightly reduce its tilt to a safer angle by soil removal 38 cubic metres (1,342 cubic feet) from underneath the raised end. The tower's tilt was reduced by 45 centimetres (17.7 inches), returning to its 1838 position. After almost 12 years of corrective reconstruction and stabilization efforts, the tower was reopened to the public on 15 December 2001, and was declared stable for at least another 300 years. In total, 70 metric tons (77 short tons) of soil were removed.

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