Brunelleschi's Dome: How a Renaissance Genius Reinvented Architecture

The dome of the Florentine cathedral could be seen as the latest iteration in humanity’s ancient quest to create large, monumental structures. Whereas many of Brunelleschi’s contemporaries criticized large structures from antiquity as evidence of humanity’s hubris, the dome of Santa Maria del Fiore was praised as “evidence of man’s God-given power to invent and the superiority of Florentine commerce and culture” (104). The people of Florence watched the dome being built brick by brick and circle by circle. The exterior shell of the dome, however, was not actually circular but octagonal. On the outside, Brunelleschi created “a kind of circular skeleton over which the octagonal structure of the dome took shape” (105). The inner dome, meanwhile, was built in a circular fashion. Horizontal arches were inserted between the two domes for safety purposes, encircling the dome at 8 foot intervals. These could be seen from the walkways which were in use between the two domes. The hoop tension of the dome above 36 braccia, when the angle of the dome exceeded 30 degrees, dictated the use of these nine rings. Though they could be seen from the inside, they were invisible to outsiders, to whom the dome still seemed octagonal.

Giovanni Battista Strozzi referred to the dome being built “circle by circle” (107) as both a reference to the construction process and an allusion to the famous circular depictions of heaven and hell in Dante Algieri’s Divine Comedy. The Florence-born Dante was one of the city’s most celebrated sons by the time of the construction of the dome. Dante’s depiction of hell, echoed in Brunelleschi’s design, foreshadowed the difficult period which would soon dominate Brunelleschi’s life.

As work on the cupola progressed through 1428, Brunelleschi faced his “first real setback” (110). More than 100 years earlier, the decision had been made to cover the exterior of the cathedral in Carrara marble. The bright white marble of Carrara was expensive and difficult to transport, especially given that the Arno—the river flowing through Florence—was not suited to large ships. Brunelleschi believed he had the answer. He was awarded a contract by the Opera del Duomo to transport 100,000 lbs of marble from Pisa to Florence. To accomplish this, he invented a new type of boat, the specifics of which are not known. For this new vessel, named Il Badalone (meaning The Monster), Brunelleschi was also awarded the world’s first patent, for “some machine or kind of ship, by means of which he thinks he can easily, at any time, bring in any merchandise and load on the river Arno and on any other river or water, for less money than usual” (114). Descriptions of the machine are notably absent from the writings of Manetti or Brunelleschi’s other near-contemporary biographer, the painter Giorgio Vasari, likely because Il Badalone was a disastrous failure. It sank, and Brunelleschi spent years attempting to recover the marble at great personal cost. Having predicted this failure, Giovanni da Prato wrote a sonnet to mock Brunelleschi, who responded in kind. Altogether, Brunelleschi lost the equivalent of ten years of salary to the failure, as well as damage to his reputation.

While Il Badalone weighed anchor and the workers at the dome labored 270 feet above ground, the Opera del Duomo was increasingly convinced of Brunelleschi’s plan to build the dome without centering. They had bought so completely into Brunelleschi’s plans that the once-revered model of the cathedral built by Neri di Fioravanti was repurposed as a lavatory. When cracks appeared in the side walls, however, work was paused. Brunelleschi proposed a series of chapels to be built alongside the cathedral to help support and buttress the building. While he was planning this proposal, however, Florence was distracted by war.

Brunelleschi was sent to the town of Lucca, 40 miles from Florence. The Republic of Florence had attacked Lucca, and a period of relative peace was coming to an end. In Milan, Giangaleazzo’s son Filippo Maria Visconti had resumed his father’s ambitious war. The Florentines accused the rulers of Lucca of forming a secret pact with Visconti, so they sent Brunelleschi to use his engineering expertise to end the siege. Military commissions were common for men like Brunelleschi, but such men were usually tasked with engineering defensive measures. Brunelleschi had never planned an offensive, and his plans were “much more ambitious” (125) than anything he had undertaken before. He planned to alter the course of the Serchio River with a dam and thus isolate Lucca in the middle of a lake. Brunelleschi, as usual, ignored advice and criticisms.

The dam was a failure. The Lucca forces attacked it and burst it before completion, flooding instead the Florentine encampment and destroying the Florentine army. Florence lost a decisive battle and an important strategic asset. Brunelleschi was not solely blamed, however, as many blamed “homosexuality” (129), which was allegedly a fundamental part of Florentine life. In 1432, the Florence government acted against this widespread homosexuality in an effort to end their supposed bad luck. A peace treaty with Milan was signed in 1433, much to the embarrassment of Florence.

The war in Lucca was not just personally embarrassing for Brunelleschi. It also affected the construction of the dome, as workers’ wages were halved. Brunelleschi’s own wages were cut. His plan to surround the cathedral with a series of chapels was also rejected in favor of a cheaper option, reinforcing the cracked parts of the cathedral wall with iron rods. Brunelleschi showed his contempt for this by delaying and delaying the work until he was ordered to complete it. His concerns were soon overshadowed, however, when he was arrested and thrown in prison.

Brunelleschi was charged with not paying his dues to the Guild of Stonemasons and Carpenters. Many members of the guild were in arrears on these payments, suggesting that his arrest was politically motivated. At this point, Brunelleschi was “rapidly falling out of favor with the Florentine ruling class” (133). Cosimo de’ Medici, the patriarch of the powerful Medici family and a supporter of Brunelleschi, had been sent into exile. King suggests that Brunelleschi’s diminished status and repeated failures created an opportunity for old rivals such as Ghiberti to pounce. Brunelleschi, however, was not treated like a common criminal, and he was soon freed by the Opera del Duomo. The day after his release, a pro-Medici government was elected and Cosimo also returned.

Two months later, Brunelleschi’s adopted son Andrea Cavalcanti, known as Il Buggiano, ran away to Naples with Brunelleschi’s money. He had followed in his adoptive father’s footsteps and was regarded as a skilled artist. He worked often for his father, but he was often paid late or not at all. Brunelleschi was negligent toward his finances, and his failure to pay his taxes on time made him ineligible for election to the Florentine government on several occasions. Fortunately for Brunelleschi, Pope Eugenius IV was residing in Florence during this time to avoid civil unrest and war in Rome. At Brunelleschi’s request, the Pope wrote to the government in Naples and Il Buggiano was returned, together with the stolen jewels. Brunelleschi welcomed back his adopted son, who was later made his heir.