Timeline
What year did Giorgio Vasari write "Guglielmo" ?
Leaning Tower of Pisa
 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.  On August 9, 1173, the foundations of the Tower were laid.  Nearly four centuries later Giorgio Vasari wrote: "Guglielmo, according to what is being said, in year 1174 with Bonanno as sculptor, laid the foundations of the bell tower of the cathedral in Pisa. "  Giorgio Vasari indicates that Tommaso di Andrea Pisano was the designer of the belfry between 1360 and 1370.  On December 27, 1233, the worker Benenato, son of Gerardo Bottici, oversaw the continuation of the construction of the bell tower.  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.  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.