<P> The cathedral complex, in Piazza del Duomo, includes the Baptistery and Giotto's Campanile . These three buildings are part of the UNESCO World Heritage Site covering the historic centre of Florence and are a major tourist attraction of Tuscany . The basilica is one of Italy's largest churches, and until the development of new structural materials in the modern era, the dome was the largest in the world . It remains the largest brick dome ever constructed . </P> <P> The cathedral is the mother church of the Roman Catholic Archdiocese of Florence, whose archbishop is currently Giuseppe Betori . </P> <P> Santa Maria del Fiore was built on the site of Florence's second cathedral dedicated to Saint Reparata; the first was the Basilica di San Lorenzo di Firenze whose first building was consecrated as a church in 393 by St. Ambrose of Milan . The ancient structure, founded in the early 5th century and having undergone many repairs, was crumbling with age, according to the 14th - century Nuova Cronica of Giovanni Villani, and was no longer large enough to serve the growing population of the city . Other major Tuscan cities had undertaken ambitious reconstructions of their cathedrals during the Late Medieval period, such as Pisa and particularly Siena where the enormous proposed extensions were never completed . </P> <P> The new church was designed by Arnolfo di Cambio and approved by city council in 1294 . Di Cambio was also architect of the church of Santa Croce and the Palazzo Vecchio . He designed three wide naves ending under the octagonal dome, with the middle nave covering the area of Santa Reparata . The first stone was laid on September 9, 1296, by Cardinal Valeriana, the first papal legate ever sent to Florence . The building of this vast project was to last 140 years; Arnolfo's plan for the eastern end, although maintained in concept, was greatly expanded in size . </P>

How did they build the duomo in florence