The Dome of Florence Cathedral
For a long time the cathedral of Santa Maria del Fiore had a hole where the dome was to go – nobody knew how to vault a span of some 45 metres. Brunelleschi won the competition and built two shells of brick laid in herringbone bond, in which each ring supported itself, without scaffolding from the floor. The dome became the symbol of the Renaissance.
The cathedral was begun in 1296 to designs by Arnolfo di Cambio, and in the 1360s it was decided that the crossing should be covered by an enormous octagonal dome, without visible flying buttresses. Nobody knew how it could be built. The wool merchants’ guild, which was responsible for the building, announced a competition in 1418. Filippo Brunelleschi, a goldsmith by training, proposed building the dome without the timber centring that was normally required. He and Lorenzo Ghiberti were appointed to direct the work, but it was Brunelleschi who was in charge. The dome was built between 1420 and 1436, when it was consecrated. To raise the building materials Brunelleschi designed an ox-driven hoist that could lift and lower without the animals having to be turned round, an invention that aroused great admiration.
The dome consists of two shells, a thicker inner one and a thinner outer one, with a cavity between them in which stairs lead up to the top. Eight large ribs at the corners and hidden intermediate ribs tie the shells together, and rings of stone, iron and timber hold the structure together like the hoops of a barrel. The bricks are laid in a herringbone pattern, so that each new course was held in place by the vertical bricks while the mortar set. The profile is pointed, because such a shape pushes outwards less than a hemispherical one. The dome rests on an octagonal drum with round windows. The marble lantern was designed by Brunelleschi but completed after his death. Inside is a vast painting of the Last Judgement from the 1570s by Giorgio Vasari and Federico Zuccari.
The dome has stood for almost six hundred years, but cracks in the masonry have been closely monitored since the 17th century and are now measured with modern instruments. A gallery intended to run around the base of the dome was begun in the early 16th century but was built on only one of the eight sides. The copper ball on the lantern was made in the 1470s in Verrocchio’s workshop, where the young Leonardo da Vinci was working at the time. Brunelleschi’s dome showed that a modern architect could rival antiquity and became the symbol of the Renaissance. It influenced Michelangelo’s dome over St Peter’s, Wren’s St Paul’s and later the Capitol in Washington. For everyone who studied architecture it became an example of how engineering and artistic ambition go hand in hand.