Major Duomo

Opera di Santa Maria del Fiore, Florence/photo Claudio Giovannini
Duomo, Florence

Major Duomo

By Roderick Conway Morris

FLORENCE 6 November 2020

This year marks the 600th anniversary of one of the most stupendous events in architectural history: the beginning of work on the great dome for Santa Maria del Fiore, Florence's Cathedral known as the Duomo, which still dominates the city's skyline. The genius responsible was Filippo Brunelleschi (1377-1446) who, during the same period, left a second great gift to posterity: the invention of mathematical, or measured, perspective.

The building of Santa Maria del Fiore was begun in 1296. In an extraordinary leap of faith, the original plan included an octagonal drum 45 metres (nearly 150 feet) in diameter, designed to support a vast dome - the sole problem being that no technology existed at that time to realize such a structure on this scale, rising from a base 55 metres (180 feet) above the ground. Indeed, the Florentines would have to wait for over 120 years for the sculptor-architect-engineer Filippo Brunelleschi to find a solution to this seemingly impossible challenge.

A goldsmith by training, Brunelleschi turned to architecture after being narrowly defeated in 1401 by Lorenzo Ghiberti in the competition to design the second set of massive bronze doors for the old octagonal Baptistery in front of the Cathedral's west end. He took himself off to Rome to study the ancient monuments there. The essential outline of the required cupola had already been established, and when a competition was held in 1418 to build it, Brunelleschi stepped forward, now describing himself as an expert on ancient domes.

Although remaining cagey about important technical details of his plan, fearing they would be stolen by rivals, Brunelleschi won the commission with his proposal to construct two concentric octagonal domes, an internal and external one, supported by visible and invisible ribs creating eight arches, each 85 feet across. In fact, the inspiration for these was more gothic than Roman. Many other aspects of the design were entirely without precedent and a number have remained a mystery, even to modern analysts. Original features included a series of ascending circular ties made of wood and stone, locked together with iron links, hidden between the inner and outer domes, that held the cupola together internally like the exterior hoops of a barrel.

Since there was no traditional ground-based type of scaffolding that could be built to a sufficient height to support the dome while it was being built, Brunelleschi conceived a new form of suspended scaffolding consisting of oak beams inserted into sockets around the inner wall of the dome, like spokes of a wheel, with planks laid on them to create a circular working platform.

A large opening in the middle allowed building materials to be hoisted aloft by a powerful, specially designed crane, driven by oxen circling on the cathedral floor scores of feet below. To support the exterior tiled dome, the inner dome was made of some four million bricks, arranged in a herringbone pattern to lock them into place. Brunelleschi's scaffolding system proved so safe that during the sixteen years of the dome's construction there was only one fatal accident.

The architect's large wooden model for the dome can still be seen at the superb new Museo dell'Opera del Duomo - along with original brick forms, tools, ropes and scaffolding - which occupies a site on Piazza del Duomo that was once the architect's construction yard and location of the ovens where the bricks were fired.

In 1436, the dome completed, the Cathedral was consecrated by Pope Eugene IV on 25 March, Feast of the Annunciation and beginning of the year in the old Florentine calendar. Brunelleschi also designed the marble lantern, as tall as a five-storey building, on the summit of the dome, the downward thrust of its weight ensuring the long-term stability of the entire structure. The lantern was only completed after the architect's death, and the finishing touch, the great gilded brass sphere and cross, twenty years later.

It seems that Brunelleschi began to elaborate his system of mathematical perspective while undertaking surveys of ancient monuments in Rome and seeking accurate methods of recording their heights and widths, skills that he later applied in building the Duomo's cupola. The surveying methods he developed were then applied to making perspective drawings and paintings according to a mathematically calculated system.

By the 14th century, 'perspective' was already being classified by scholars as 'practical geometry', of the kind described in the ninth-century Islamic treatise by Al Farabi (available in Latin) as a method of measuring 'the height of trees and walls, the broadness of rivers, the depth of valleys, the height of mountains'. But the challenge to Brunelleschi was to translate these techniques of measurement and other geometrical formulas into a representational system capable of creating a seemingly three-dimensional image on a flat or low-relief surface.

A simple aid for reducing a 3-D object to a flat-surface image was a mirror, whose use by artists was attested by ancient sources. One of Brunelleschi's demonstrations of his use of perspective in painting employed an easel-like device placed some distance from the Baptistery, on which his painting of the building, facing away from the viewer, was reflected back by a mirror.

The distance between the mirror and the painting was measured out in proportion to the distance between the observer and the Baptistery, so that when the observer peered at the Baptistery through a small aperture and then slid the mirror in front of the building, the reflected image appeared to be exactly the same size as the actual building.

The successful perspective rendering of the classical architectural setting of Masaccio's Trinity fresco of 1426-27 in the Santa Maria Novella church in Florence, in the creation of which Brunelleschi collaborated, established it as a landmark in the history of painting. Indeed, Brunelleschi's invention of mathematical perspective had enormous implications not only for drawing, painting and architectural design, but also illusionistic theatrical scenes, terrestrial and celestial mapmaking and more warlike pursuits such as making surveys from a distance of enemy fortifications and calculating ranges for artillery.

First published: The Lady