The Leaning Tower of Pisa has an amazing history. After construction began on it in 1173, one side of the tower started sinking into the ground, even before it was completed. It was finally finished almost 200 years later and in the 1830s excavation work near the tower destabilized the foundation and it sank even further.
It wasn’t until 1989, when another tower in Italy collapsed, that the Italian government finally closed it to tourists to prevent its collapse. Then they got down to trying to figure out how to fix the issue. Drilling holes to make the structure lighter was brought up, as was building another tower, leaning the opposite way to hold it up!
The final solution was to sink the high side. They used 100 tons of weight and steel cables to prevent further leaning, then drilled dirt out. After three years they were able to reduce the angle of leaning by half a degree. The steel cables were then removed. According to the report at Wired, engineers have determined that it is at the same tilt now that it was around 300 years ago and that it won’t need any further work for another few hundred more.
[Image: Carlo Alcos]