The Tower of Pisa is the bell tower of the Cathedral. Its construction began in the august of 1173 and continued (with two long interruptions) for about two hundred years, in full fidelity to the original project, whose architect is still uncertain. In the past it was widely believed that the inclination of the Tower was part of the project ever since its beginning, but now we know that it is not so. The Tower was designed to be vertical (and even if it did not lean it would still be one of the most remarkable bell towers in Europe), and started to incline during its construction. Both because of its inclination, and its beauty, from 1173 up to the present the Tower has been the object of very special attention. During its construction efforts were made to halt the incipient inclination through the use of special construction devices; later colums and other damaged parts were substituted in more than one occasion; today, interventions are being carried out within the sub-soil in order to significantly reduce the inclination and to make sure that Tower will have a long life. In all this story it is possible to find a meaningful constant, the genetic code of the Tower: its continual interaction with the soil on which it was built. Todays (1999) works for the safeguard and the conservation of the Tower with very advanced methodologies are designed to fully respect this constant 比萨斜塔可能是全意大利最美丽的钟楼。这座塔有八层.有 54.5 米高，294 级台阶到塔顶，从塔顶能看到非常美丽的景色。可是，它也是世界上最奇怪的塔。它向一边倾斜，看起来好像随时会倒塌。
