Why doesn't the Leaning Tower of Pisa fall over?

In 1990, the Italian government enlisted top engineers to stabilize Pisa's famous Leaning Tower. There'd been many attempts during its 800 year history, but computer models revealed the urgency of their situation. The tower would topple if it reached an angle of 5.44 degrees— and it was currently leaning at 5.5. What gives the tower its infamous tilt? Alex Gendler explores the monument's history. [Directed by Aim Creative Studios, narrated by Addison Anderson, music by André Aires].