The Leaning Tower of Pisa, peering over the shoulder of the Pisa Cathedral. The Leaning Tower is pretty much the star of Pisa and the reason why this little town is perennially flooded with visitors. This curious bell tower was never intended to tilt, but began to do so during its construction. The subsoil it was built on was too soft to support its weight on one side. Over a century in its original construction, it took modern engineers decades further to stabilize and preserve the tilt. Today, a climb up this historic monument will set you back about €15.