The dome that covers the Florence cathedral (the church of Santa Maria del Fiore) is known as Filippo Brunelleschi’s dome. When it was designed, it was the largest dome in the world. This immediately created problems as its size prevented the traditional method of construction. Its structure is a double shell supported by sturdy pillars.
Imagine the thriving city of Florence in the year 1296. Proud of their city, the Florentines began to build a glorious cathedral, reserving enough space in its design for a huge dome. But there was one problem: no one knew how to erect a dome that would be nearly 150 feet wide and that would begin 180 feet above the ground, atop the existing walls.
Other questions plagued the cathedral overseers. Their building plans eschewed the flying buttresses and pointed arches of the traditional Gothic style then favored by rival northern cities like Milan, Florence’s arch enemy. Yet these were the only architectural solutions known to work in such a vast structure. Could a dome weighing tens of thousands of tons stay up without them? Was there enough timber in Tuscany for the scaffolding and templates that would be needed to shape the dome’s masonry? And could a dome be built at all on the octagonal floor plan dictated by the existing walls—eight pie-shaped wedges—without collapsing inward as the masonry arched toward the apex? No one knew.
When was the dome of the Florence cathedral built?
In 1418 the Opera del Duomo announced a public competition for the construction of the dome with a handsome prize of 200 gold florins—and a shot at eternal fame—for the winner. Leading architects of the time flocked to Florence to present their ideas.
After many uncertainty the Opera del Duomo agreed to make Filippo Brunelleschi the superintendent of the cupola project and appointed Lorenzo Ghiberti, Brunelleschi’s fellow goldsmith, as a co-superintendent. The two men had been rivals since 1401, when they had vied for another illustrious commission, the new bronze doors for the Florentine Baptistery. Ghiberti had won. Now Brunelleschi, whose design for the cupola had been accepted outright, was forced to work side by side with his gallingly successful rival.
The construction of the Dome began on 7 August 1420.
Here some guided tours of the Brunelleschi’s dome and the Florence cathedral:
The Brunelleschi’s project
The usual way to build an arch or dome was to support it with scaffolding called “centring.” However, the open space in the cathedral was 42 metres wide, and the Florentines wanted a tall, soaring dome.
All the timber in Tuscany would not have sufficed to make the centring.
Brunelleschi ended up building the dome without scaffolding in such a way that it supported itself as the work progressed.
Brunelleschi’s solutions for the dome were ingenious, innovative, and expensive.
The first problem to be solved was purely technical: no known lifting mechanisms at the time were capable of raising and maneuvering the enormously heavy materials he had to work with, including sandstone beams, so far off the ground. Here Brunelleschi outdid himself.
He invented a three-speed hoist with an intricate system of gears, pulleys, screws, and driveshafts powered by a single yoke of oxen turning a wooden tiller and the castello, a 65-foot-tall crane with a series of counterweights and hand screws to move loads laterally once they’d been raised to the right height.
The octagonal shape of the dome is definitely inspired by that of the Baptistry.
The whole structure of the dome is designed to be light and slim in both form and substance. In fact, from an octagonal drum of the dome stand eight segments, the sails, arranged on two shells separated by a space. Brunelleschi wove regular courses of herringbone brickwork, little known before his time, into the texture of the cupola, giving the entire structure additional solidity.
Throughout the years of construction Brunelleschi spent more and more time on the work site. He oversaw the production of bricks of various dimensions and attended to the supply of choice stone and marble from the quarries. He led an army of masons and stonecutters, carpenters, blacksmiths, lead beaters, barrelmakers, water carriers, and other craftsmen.
Chief among the elements that make up the dome is its use of the golden proportion, which was in vogue at the time. In contemplating this masterpiece, you notice that its builders have made use of balance and harmony between each of its parts. Each architectural element contributes to the stability of the dome as it stands without supporting structures.
Another of these crucial elements is the lantern, on top of which rests the bronze ball built by Verrocchio in 1472. To position the ball they used machines invented by Brunelleschi. The young Leonardo da Vinci figured among the apprentices that helped in this difficult operation.
The dome is a masterpiece of beauty and engineering, a pioneering construction for its time, and in many ways remains unmatched.
As a master of illusions, Brunelleschi was known in Florence to have made people believe in things that did not exist. The construction of its dome sparked years of debate on what was the “magic trick that provided the result that lay in front of everyone, i.e., how the octagonal dome was able to stand!
Even today, although extensive studies have been carried out and many new discoveries have been made, there is still a debate on what was the ingenious solution found by the architect Filippo Brunelleschi.
On March 25, 1436, the Feast of the Annunciation, Pope Eugenius IV and an assembly of cardinals and bishops consecrated the finished cathedral to the tolling of bells and cheering of proud Florentines. A decade later, another illustrious group laid the cornerstone of the lantern, the decorative marble structure that Brunelleschi designed to crown his masterpiece.
Soon after, on April 15, 1446, Brunelleschi died, apparently from a sudden illness. He was buried in the crypt of the cathedral; a memorial plaque nearby celebrated his “divine intellect. These were high honors. Before Brunelleschi’s time, very few people, among them a saint, were allowed burial in the crypt.
A part of the dome remains unfinished when Brunelleschi died: the upper part of the drum.
The competition to build this section was won by the Italian woodcarver, sculptor and architect Baccio d’Agnolo.
Construction of the drum began but according to tradition, Baccio decided at some point to seek the opinion of the people of Florence.
Michelangelo Buonarroti, who was in town at the time, was of course asked the question. Looking at the work he exclaimed: “It looks like a cricket cage! Offended, Baccio d’Agnolo left the drum unfinished, just as we see it today.
The dome ceiling
The painting of the dome on the inside began in 1572 when the Grand Duke Cosimo I de’ Medici commissioned Giorgio Vasari to paint frescoes on the dome. Vasari was flanked by Vincenzo Borghini, who worked on the iconographic subjects and added other themes taken from Dante’s Divine Comedy
The dome is decorated with a magnificent cycle of frescoes depicting the Last Judgement.
After the death of Giorgio Vasari in 1574, Federico Zuccaro, an artist from Urbino, completed the frescoes around 1575-79.
High up on the fresco in the dome, around the cupola, hovers a temple with the twenty-four elders of the Apocalypse; beneath this, on terraced registers, follow choirs of angels with the instruments of the Passion; groups of saints; personifications of the gifts of the Holy Spirit, of the virtues, and of the beatitudes; and finally, the regions of hell with various deadly sins. The composition of the fresco thus takes into account the architectonic form of the vault in its eight sections, hard upon one another.
These frescoes can be seen very well on the way up to the dome.
How an amateur built the world’s biggest dome
Here a National Geographic video illustrating how Brunelleschi built the dome:
This post was originally published on November 18, 2013, and has been updated and enriched on September 19, 2016, and on June 16, 2019.