The iconic symbol of Italy, Pisa's bell-tower would be a beautiful and architecturally significant building even without its famous lean. Rising eight storeys above the aptly named Campo dei Miracoli - the field of miracles - the tower was used by Galileo in his experiments on gravity.
Take a closer look at the cathedral and the other buildings on the Campo dei Miracoli and you'll notice that none of them are perpendicular to the ground either.