Why go
The cathedral is easier to read as a long civic project than as one architect's achievement. After Arnolfo di Cambio's death, work slowed until the wool guild took charge in 1331 and appointed Giotto. The Black Death interrupted construction, and the decisive dome challenge came only in the 15th century. That sequence explains why the cathedral, campanile and dome carry different architectural voices.
The full story
Work slowed after Arnolfo di Cambio died in 1310, then revived after the relics of Saint Zenobius were found at Santa Reparata in 1330. In 1331 the Arte della Lana, Florence's wool guild, assumed patronage. It appointed Giotto in 1334, and his principal contribution was the campanile. Andrea Pisano continued after Giotto's death, before the Black Death stopped work in 1348. The unfinished building later required a dome unlike any then standing. A 1367 design called for an octagonal, unbuttressed structure with an inner and outer shell, but did not yet solve the forces that would make it spread. Brunelleschi and Lorenzo Ghiberti were appointed to the project; Brunelleschi's construction method ultimately completed the challenge. This long handover of responsibility is visible in the ensemble's varied forms.