Pisa's Torre Pendente (Leaning Tower) is, perhaps, the most famous tower in the world. The tower is the campanile (bell tower) of the cathedral and the first stone was laid on August 9th, 1173, as proclaimed in an inscription to the right of the entrance.
The bell tower, whose original architect remains unknown, was only 10 metres high (third ring) when subsidence (and inadequate foundations) threw it off the perpendicular. Construction stopped, only to resume a century later, in 1272, under Giovanni di Simone, who added three more rings. By 1284 the tower had risen as high as the bell chamber, which was added between 1350 and 1372 by Tommaso di Andrea Pisano.
The height of the bell tower is 55.86 metres (183 feet) on the low side and 56.67 metres (186 feet) on the high side. The tower leans at an angle of 3.9 degrees, which means that it is 3.9 metres (13 feet) off the vertical. Prior to its restoration (1990-2001) it leaned at an angle of 5.5 degrees.
The entrance to the tower is flanked by zoomorphic reliefs, while another relief depicts the Entrance to the Harbour of Pisa.
The bell tower has wryly been described as a ‘column of columns’.