Even before it was finished 800 years ago, the Leaning Tower of Pisa - a masterpiece of medieval architecture - began to topple, shaken by earthquakes and sinking slowly into the unstable soil. Today, the top hangs just 16 feet over the base and collapse seems imminent. NOVA follows a decade-long search for a solution to correct the lean and save the unique building. State-of-the-art computer models, ingenious experiments with... see more