ABSTRACT
The bell-tower of Pisa Cathedral is admired for its architectural beauty, but it is especially famous by its disconcerting tilt, which had developed over more than eight centuries until being stabilized by a delicate and ingineous intervention concluded in 2001. The tower was built in three stages. From 1173 to 1178, the foundation and the first four floors were constructed, reaching 29 m height. The works were then halted for nearly a century. From 1272 to 1278, the tower was built to the seventh loggia, rising to 51 m in height. Another stoppage followed, lasting about eighty years. Finally, from 1360 to 1370 the tower was completed, with the addition of the bell-chamber, reaching a height of 58 m. The tower was already inclined when the second construction phase started. The builders attempted to correct the shift from the vertical along the three subsequent stories by placing more masonry blocks on the south side.
