Traffic and people gravitate towards the square at the heart of Florence, Piazza del Duomo, beckoned by the pinnacle of Brunelleschi’s extraordinary dome, which dominates the cityscape in a way unmatched by any architectural creation in any other Italian city. Yet even though the magnitude of the Duomo is apparent from a distance, the first full sight of the church and the adjacent Baptistry still comes as a jolt, the colours of their patterned exteriors making a startling contrast with the dun-coloured buildings around them.
It was sometime in the seventh century when the seat of the Bishop of Florence was transferred from San Lorenzo to the ancient church that stood on the site of the Duomo. In the thirteenth century, it was decided that a new cathedral was required, to better reflect the wealth of the city and to put the Pisans and Sienese in their place. In 1294 Arnolfo di Cambio designed a vast basilica focused on a domed tribune; by 1418 this project was complete except for its crowning feature. The conception was magnificent: the dome was to span a distance of nearly 42m and rise from a base some 54m above the floor of the nave. It was to be the largest dome ever constructed – but nobody had yet worked out how to build it.
A committee of the masons’ guild was set up to ponder the problem, and it was to them that Filippo Brunelleschi presented himself. Some seventeen years before, in 1401, Brunelleschi had been defeated by Ghiberti in the competition to design the Baptistry doors, and had spent the intervening time studying classical architecture and developing new theories of engineering. He won the commission on condition that he worked jointly with Ghiberti – a partnership that did not last long. The key to the dome’s success was the construction of two shells: a light outer shell about one metre thick, and an inner shell four times thicker. On March 25, 1436 – Annunciation Day, and the Florentine New Year – the completion of the dome was marked by the papal consecration of the cathedral.
The Duomo’s overblown main facade is a nineteenth-century imitation of a Gothic front, its marble cladding quarried from the same sources as the first builders used – white stone from Carrara, red from the Maremma, green from Prato. The south side is the oldest part, but the most attractive adornment is the Porta della Mandorla, on the north side. This takes its name from the almond-shaped frame that contains the relief The Assumption of the Virgin, sculpted by Nanni di Banco around 1420.
The Duomo’s interior is a vast enclosure of bare masonry that makes a stark contrast to the fussy exterior. Initially, the most conspicuous pieces of decoration are two memorials to condottieri (mercenary commanders) in the north aisle – Uccello’s monument to Sir John Hawkwood, painted in 1436, and Castagno’s monument to Niccolò da Tolentino, created twenty years later. Just beyond, Domenico do Michelino’s Dante Explaining the Divine Comedy makes the dome only marginally less prominent than the mountain of Purgatory. Judged by mere size, the major work of art in the Duomo is the fresco of The Last Judgement inside the dome; painted by Vasari and Zuccari, it merely defaces Brunelleschi’s masterpiece. Below the fresco are seven stained-glass roundels designed by Uccello, Ghiberti, Castagno and Donatello; they are best inspected from the gallery immediately below them, which forms part of the route up inside the dome – the entrance is outside, on the north side. The gallery is the queasiest part of the climb, the last part of which winds between the brick walls of the outer and inner shells of the dome; the views from the summit, are you'd expect, are stunning.
In the 1960s remnants of the Duomo’s predecessor, Santa Reparata, were uncovered beneath the west end of the nave. A detailed model helps make sense of the jigsaw of Roman, early Christian and Romanesque remains, areas of mosaic and patches of fourteenth-century frescoes. Also down here is the tomb of Brunelleschi, one of the few Florentines honoured with burial inside the Duomo.