Florence built a cathedral with a gaping hole where its dome should be
By the early 1400s Florence's cathedral had been rising for a century, yet it still had no roof over its crossing. The planned octagonal dome was wider and taller than anything ever raised, and it was forbidden to use buttresses. Filippo Brunelleschi found a way, and his brick dome remains the largest in masonry.
Work began on 9 September 1296 to a design by Arnolfo di Cambio, replacing the crumbling church of Santa Reparata. Progress stalled for nearly 50 years after Arnolfo died in 1302. The wool merchants' guild took charge in 1331 and appointed Giotto, whose lasting gift was the bell tower, and the Black Death halted work again in 1348. By 1380 the nave was done, leaving one enormous problem.
Back in 1367 the city had chosen Neri di Fioravanti's model, a dome standing on an unbuttressed octagonal drum. Florentines saw flying buttresses as ugly crutches favoured by rival northern states, so they were banned, and historians call that choice one of the first acts of the Renaissance. The catch was engineering: the dome would start 52 m above the floor and span 44 m, and Tuscany lacked enough timber for the scaffolding a Roman-style build required.
In 1418 the guild held a competition. Brunelleschi, backed by Cosimo de' Medici, beat his old rival Lorenzo Ghiberti, though the two were made joint heads on equal pay. Ghiberti's role faded, and by 1423 Brunelleschi alone was in charge. From 1420 he raised two nested shells of lightweight brick with no supporting frame beneath, reserving sandstone and marble for ribs, tension chains and the lantern. He even left his model deliberately incomplete so builders had to keep coming to him.
Pope Eugene IV consecrated the church on 25 March 1436, which was New Year's Day in the Florentine calendar. The dome reaches 114.5 m, and the whole building covers 8,300 square metres. Its marble skin of white, green and red, sourced from Carrara, Prato and Siena, took far longer: a façade contest under Lorenzo de' Medici in 1490 and 1491 fizzled, and the present front by Emilio De Fabris only arrived in 1887.
Source: Florence Cathedral
