The Leaning Tower of Pisa, right, and the Duomo basilica at celebrations marking its restoration.

Video. The Leaning Tower of Pisa celebrates its 850th birthday

Designated a World Heritage Site by UNESCO, together with the whole of Pisa's Piazza del Duomo, the tower is a fundamental example of the Romanesque style, in particular Pisan Romanesque, and a fine example of medieval engineering.