The construction of The Dome began in the summer of 1420 and was finished by 1436. The lantern, designed by Brunelleschi, was completed after his death. The copper sphere was placed on top by Verrocchio in 1472. The construction embodies a rigorously geometrical design.

The octagonal drum carries eight "shells." Empty spaces have been left inside each of these to lighten the massive structure. The angle ribs are not intended to provide structural support. Another notable feature is the external covering system, which consists of tiles specially designed for easy assembly and maintenance.