January 7, 1990
The Leaning Tower of Pisa was closed to the public after it was deemed to be leaning too far. The lean was measured at 5.5 degrees, meaning that the top of the tower is displaced horizontally 5.5 metres (or about 18 feet from where it would be if the tower were vertical).
The bells were removed to relieve some weight, and cables were cinched around the tower and anchored to the ground. Over ten years, the angle of the lean was corrected by removing soil from underneath the raised end and resituating the tower. It was therefore straightened to 3.99 degrees, meaning that the top of the tower is displaced horizontally 3.9 metres (about 13 feet from where it would be if the structure were perfectly vertical). After a decade of stabilization, the tower was reopened to the public on December 15, 2001, and was declared stable for at least another 300 years.