One of the world's most famous buildings, the Leaning Tower of Pisa, has survived everything from four powerful earthquakes to two world wars. Now, engineers may have solved the mystery of how the building has managed to survive, undamaged, for centuries.

Ironically, the reason the tower is tilted is also why it survived so long: "The very same soil that caused the leaning instability and brought the tower to the verge of collapse can be credited for helping it survive these seismic events," said George Mylonakis of the University of Bristol's department of civil engineering.