The Florence Baptistery: a building the city was wrong about for six hundred years

What the digging found

Excavations beneath the building in the early twentieth century showed that its walls do rest on Roman structures — real ones, dated to around the third century — along with a burial ground whose stones date to the seventh.

But the octagon above them is medieval. The scholarly consensus now puts construction in the eleventh or twelfth century. Walter Horn's masonry analysis in the 1930s, comparing it with San Miniato al Monte and Santi Apostoli, pointed to the 1060s or 1070s, and a 2024 argument places the origin in the early 1070s, possibly sponsored under the reforming popes with Beatrice of Lorraine and Matilda of Tuscany.

The century is settled. The decade is still being fought over.

Why the mistake was so easy to make

Look at the surface. Each of the eight faces is divided into three horizontal bands by proper classical entablatures, with blind arches and geometric inlay in white Carrara marble and the green-black serpentinite quarried at Prato. The discipline of it has nothing to do with the Gothic going up in France at the same moment.

And some of it genuinely is Roman. The large columns at ground level are spolia — taken from ancient buildings, very probably from the forum a few streets away — because nobody in eleventh-century Tuscany could quarry and dress a column that size. The two porphyry columns flanking the east door are Pisan war loot from Mallorca, given to Florence in 1117 in thanks for protection against Lucca.

The mistake had physical evidence inside it.

And the mistake built the dome

Because everyone believed this was antique, the architects of the fifteenth century studied it as antique. Brunelleschi came here repeatedly, measuring and drawing, working out how the proportions held. Some of his thinking about perspective was done on this pavement. He judged the building near perfect and is said to have found exactly one error in it: an entablature at the attic level that turns and runs vertically, which classical grammar forbids.

A false belief produced a true achievement.

1401: the competition that started everything

In 1401 the Arte di Calimala, the cloth-importers' guild that was responsible for this building, invited sculptors to submit a trial panel on a set subject — the Sacrifice of Isaac. Two of the entries survive, in the Bargello, and you can stand in front of both this afternoon.

One is by Lorenzo Ghiberti, then about twenty-three. One is by Filippo Brunelleschi.

Ghiberti won, and signed the contract at twenty-five. Brunelleschi lost, left sculpture, went to Rome to measure ruins, and came back an architect. Seventeen years later he won the competition to build the dome of the cathedral behind you.

The dome of Florence exists, in a real sense, because of a disappointment on this spot.

Three sets of doors, a hundred and twenty years apart

South doors — Andrea Pisano, 1330–36. Twenty gilded panels of the life of John the Baptist, the city's patron, each inside a four-lobed Gothic quatrefoil, with the cardinal and theological virtues below. The decorative frame around them was not finished for more than a century afterwards, by Ghiberti's son Vittorio.

North doors — Ghiberti, 1403–24. Twenty panels again, still quatrefoils, now the life of Christ — but the figures move differently: deeper relief, real foreshortening, drapery with weight. The workshop that cast them is a roll-call of the early Renaissance: Donatello, Michelozzo, Paolo Uccello, Masolino. They were hung on Easter Sunday 1424. Twenty-one years of work, revealed on the morning of the resurrection.

East doors — Ghiberti, commissioned 1425, installed 1452. Ghiberti talked the guild out of the Gothic frames altogether. Ten large rectangular panels instead of twenty small ones, gilded all over, each holding several episodes at once in genuine linear perspective. The Old Testament programme — Creation through to the Queen of Sheba meeting Solomon — was devised by Leonardo Bruni, chancellor of Florence and one of the great humanists of the age.

Michelangelo is said to have called them beautiful enough to stand at the gates of paradise. The remark comes down through tradition rather than any contemporary record, but the name stuck.

In the surrounding frame, among twenty-four prophets, Ghiberti put his own face: bald, heavy-lidded, amused. Kenneth Clark observed that the serious young man of the north doors had become a wily old bird. He gave fifty years to this one building.

The doors in front of you are copies

On 4 November 1966 the Arno flooded. Around this square the water reached about three metres. The pressure burst the east doors open and tore five panels off the Gates of Paradise.

They were recovered and restored over decades, and the conclusion was that they could not go back outside. Replicas were made between 1990 and 2009. Every original panel from all three sets is now in the Museo dell'Opera del Duomo, on the far side of the same square — a five-minute walk that almost nobody makes.

Inside: gold, and a very detailed hell

The dome carries one of the great mosaic cycles of medieval Italy, begun in the 1220s under Bishop Giovanni da Velletri and continued for decades, with Coppo di Marcovaldo among the significant hands. The subject is the Last Judgment: an enormous Christ in the vault, the saved on one side, and on the other a hell of remarkable inventiveness — devils with faces in their stomachs, sinners fed into mouths, a great deal of biting.

Every child born in Florence was christened in this building. Rich and poor came through the same door and used the same water, which makes it the most democratic room in the city. Generations of Florentine children stood on this floor and looked up at that ceiling.

Dante was one of them, baptised here in 1265. Whether the mosaic shaped the Inferno is a connection many people have drawn and nobody has proved. What is certain is that he knew this room, that he was exiled in 1302, that he never came home — and that when he wrote about returning, what he imagined was not a triumphal entry but taking the poet's laurel at the font where he was christened.

He died in Ravenna.

The font he meant is gone

For centuries the centre of the floor held a large arrangement with five basins, because Florentine babies were baptised in groups, twice a year, at Holy Saturday and Pentecost. As individual baptism became normal through the thirteenth century it stopped being needed.

In 1577 Francesco I de' Medici had it broken up to clear floor space for grand-ducal ceremonies. By all accounts the Florentines were appalled. The octagonal font still in use here is inscribed 1370.

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How long you need

Twenty minutes inside, if you let your eyes adjust — the hell only emerges after a minute or two in the dim. Then cross the square to the museum, because that is where the doors actually are.