I did not know that yesterday!

We haven't the slightest idea. To this day, the primary architect behind one of the world's most famously defective tourist attraction remains unknown. A dissertation in Yahoo's Leaning Tower of Pisa category offers several possible suspects, all of whom were famous Italian architects at the time: Bonanno, Deotiusalvi, Gerardo, Guidolotto, etc. The tower is often associated with Galileo, because of the fabled illustration of his theories on gravity: the young Galileo leaning over the balcony, the differently weighted cannon balls, their synchronous fall through the air. But while the great man did conduct some experiments on gravity in Pisa during the 16th century, he never conducted that one.

This wonderfully erratic timeline of events details the tumultuous history of the listing monolith in question. Construction started in 1173, then stops 5 years later (some trouble with the foundation, perhaps?), then recommences 100 years later, then stops after 6 years, and on and on. Why does the tower tilt? It's built on especially sandy soil, which has settled unevenly over the years.

A lot of effort has gone into straightening the tower, including an ill-advised drilling technique in 1934 that only exacerbated the problem. As it stands today, scientists and engineers are slowly but surely righting the structure to a stable angle. The aim isn't to straighten it (what's the Leaning Tower of Pisa without its lean?), but to stop it from tumbling over.