<P> The seventh floor was completed in 1319 . The bell - chamber was finally added in 1372 . It was built by Tommaso di Andrea Pisano, who succeeded in harmonizing the Gothic elements of the bell - chamber with the Romanesque style of the tower . There are seven bells, one for each note of the musical major scale . The largest one was installed in 1655 . </P> <P> After a phase (1990--2001) of structural strengthening, the tower is currently undergoing gradual surface restoration, in order to repair visible damage, mostly corrosion and blackening . These are particularly pronounced due to the tower's age and its exposure to wind and rain . </P> <Ul> <Li> On January 5, 1172, Donna Berta di Bernardo, a widow and resident of the house of dell'Opera di Santa Maria, bequeathed sixty soldi to the Opera Campanilis petrarum Sancte Marie . The sum was then used toward the purchase of a few stones which still form the base of the bell tower . </Li> <Li> On August 9, 1173, the foundations of the tower were laid . </Li> <Li> Nearly four centuries later Giorgio Vasari wrote: "Guglielmo, according to what is being said, in (this) year 1174 with Bonanno as sculptor, laid the foundations of the bell tower of the cathedral in Pisa ." </Li> <Li> On December 27, 1233, the worker Benenato, son of Gerardo Bottici, oversaw the continuation of the construction of the bell tower . </Li> <Li> On February 23, 1260, Guido Speziale, son of Giovanni, a worker on the cathedral Santa Maria Maggiore, was elected to oversee the building of the tower . </Li> <Li> On April 12, 1264, the master builder Giovanni di Simone and 23 workers went to the mountains close to Pisa to cut marble . The cut stones were given to Rainaldo Speziale, worker of St. Francesco . </Li> <Li> Giorgio Vasari indicated that Tommaso di Andrea Pisano was the designer of the belfry between 1360 and 1370 . </Li> </Ul> <Li> On January 5, 1172, Donna Berta di Bernardo, a widow and resident of the house of dell'Opera di Santa Maria, bequeathed sixty soldi to the Opera Campanilis petrarum Sancte Marie . The sum was then used toward the purchase of a few stones which still form the base of the bell tower . </Li>

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