Constructed in 1174, at a time when the Pisans were enjoying an era of military success, the Leaning Tower of Pisa, located in Pisa's Campo dei Miracoli (Field of Miracles) is famous not only because of its striking beauty but also because of its awkward geometry.
It served as the bell tower of the equally impressive Cattedrale (Cathedral) and Battistero (Baptistry), and, as a result of the poor swampy soil beneath, has leaned almost since construction first started. Today, one side is five meters (16ft) closer to the ground than the other.
Galileo used the tower for experiments to prove his theory of motion whilst he was chair of mathematics at the Universita di Pisa (Pisa University) in 1589.