Brunelleschis Dome (24 page)

There are now 463 steps to the summit. Tourists begin their climb in the southwestern pier, passing first through the Porta dei Canonici and then through a much smaller door bearing an
agnus dei
, the emblem of the Wool Guild. The first 150 steps lead to the top of this pier, spiraling counterclockwise and thus allowing for a clockwise descent, which the masons, weary after a day’s work, would have found less disorienting. It was these 150 steps that in 1418 defeated the
capomaestro
Giovanni d’Ambrogio, with whom every panting tourist can sympathize: he was sacked for being unable to climb them in order to inspect the workmanship.

The steps through the southwestern pier eventually lead onto an interior balcony that encircles the base of the dome. It was at this height that the masons held their small feast of bread and melons in the summer of 1420. From this vantage point they must have realized the magnitude of the task before them, because nowhere does the span of the dome seem greater than here, where you can gaze across the huge, echoing void. The vast interior of the vault that soars overhead is now decorated by one of the world’s largest frescoes, Vasari’s
Last Judgment
, with its gesticulating skeletons and gargantuan, pitchfork-wielding demons.
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Filippo anticipated the execution of this fresco, and iron rings from which scaffolding could be hung were inserted into the interior of the inner shell. The shell is also pierced by small windows through which a painter could crawl onto the hanging platform and begin work with his brushes.

From the interior balcony a small door leads into the gradually narrowing space between the two shells, where another set of steps threads its way upward. These steps were constructed at the same time as the cupola itself. Still remarkably unworn after more than five centuries of use, they were built out of sandstone beams delivered from the Trassinaia quarry. To the right of the staircase, sloping gently inward, is the plastered surface of the inner dome, while the outer shell runs overhead in a parallel arc. Between these two tilting walls is a disorienting maze of low doorways, cramped passageways, and irregularly ascending staircases that make the ascent a little like stepping into an Escher lithograph. It seems ironic that the first building built in the “Renaissance style” — this dome that is outwardly so ordered and graceful — should have at its core such a bewildering labyrinth of musty corridors.

It is in this confusing and constricted space between the two domes that you can see at close hand the techniques used by Filippo and his masons. In the places where the plaster on the inner dome has fallen away, the herringbone pattern is exposed to view, its elongated bricks rubbed smooth as glass by many thousands of passing hands. In other places the transverse beams of the stone chains can be seen crossing overhead like thick rafters. Part of the wooden chain is visible too. Its timbers are low enough for the present-day visitor to touch, though the original chestnut beams were replaced during the eighteenth century after they began to rot.

One of the most striking features of the climb is the series of small round windows that pierce the outer shell like portholes. These apertures bring light and air into the passages of dank stone, and through them you catch brief glimpses of the higgledy-piggledy rooftops of Florence as they recede ever farther below. These windows, of which there are seventy-two in all, form part of Filippo’s method of windproofing the dome, an attempt to protect the structure from high winds in the same way that damage to houses from tornadoes can be limited by opening their doors and windows. On blustery days the wind can be heard whistling through their openings.

A final set of steps (above which the outer shell has been cut back to allow for more headroom) leads to the octagonal viewing platform at the base of the lantern. It comes as a mild shock, having passed through the echoing, disorienting passages, then suddenly to emerge outdoors, amid wind and light, high above the ground, with a dizzying panorama of Florence and the surrounding hills at your feet. The buttresses of the lantern loom overhead like marble tree trunks, and from this proximity it is possible to see the immense size of their 5,000-pound blocks, as well as the precision with which the marble has been cut and fitted together. Stepping closer to the edge of the viewing platform, you can see the tiled sides of the dome fall dramatically away. And from this spot another advantage of the
quinto acuto
profile becomes evident: the steep rise means you can see almost directly into the piazza below — and by the same token most of the dome, including the lantern, is visible at close range from the ground.

Today tourists linger for ten or fifteen minutes on the platform before beginning their descent (some of them carrying the cupola-shaped umbrellas that are sold in Florence’s market stalls). They spend their time taking photographs, pointing out familiar landmarks, or even surreptitiously inscribing their initials on the buttresses of the lantern, which are now covered with graffiti. For most of them the climb is a means to an end, an ordeal that must be suffered in order to gain a panoramic view of the city. But centuries ago this long ascent was made by a somewhat more interested party. In the late 1540s, after being named architect in chief of St. Peter’s, Michelangelo, by then an old man, was given three passes into the cupola so that he and two of his assistants could inspect Filippo’s methods of construction before beginning work on the drum and dome of St. Peter’s. A proud Florentine, Michelangelo claimed that he could equal Filippo’s dome but never surpass it. In fact he did not even equal it, for the cupola of St. Peter’s, completed in 1590, is almost ten feet narrower and, arguably, much less graceful and striking.

Indeed, in height and span the cupola of Santa Maria del Fiore has never really been surpassed. Sir Christopher Wren’s cupola for St. Paul’s Cathedral in London, with a diameter of 112 feet, is smaller by 30 feet, and a more recent dome, that of the Capitol in Washington, D.C., is only 95 feet in span, less than two-thirds the size of the one in Florence. Not until the twentieth century were wider vaults raised, and then only by using modern materials like plastic, high-carbon steel, and aluminum, which have permitted the construction of vast tentlike structures such as the astrodome in Houston or the lightweight, prefabricated geodesic domes of Buckminster Fuller. Even so, it is no coincidence that, like Michelangelo, the master of large-scale concrete vaulting in the twentieth century, Pier Luigi Nervi, made a technical examination of Santa Maria del Fiore in the 1930s before developing the vaulting techniques he used in structures such as the Vatican audience hall and the Palazzo dello Sport in Rome. It seems wholly appropriate that this masterpiece executed by Filippo, the “treasure hunter” who once surveyed the ruins of Rome, should have become an object of study by the generations of architects who followed him.

The effect of the dome has been eloquently described by Alberti in
Della tranquillità dell’animo
, his dialogue on the tranquillity of the soul. Here he has the disillusioned politician Agnolo Pandolfini — the man who finds solace for his troubled mind in fantasies about gigantic hoists and cranes — compare the state of spiritual calm to the peaceful interior of Santa Maria del Fiore, through which he strolls with his companion Nicola de’ Medici, the failed banker. For Agnolo, the cathedral is an example of grace under pressure, of an ability to withstand the blows of fortune that he compares to adverse weather conditions that buffet the walls of the building but leave the beautiful interior pacific and unruffled:

Within, one breathes the perpetual freshness of spring. Outside there may be frost, fog or wind, but in this retreat, closed to every wind, the air is quiet and mild. What a pleasant refuge from the hot blasts of summer and autumn! And if it is true that delight resides where our senses receive all that they can demand of nature, how can one hesitate to call this temple a nest of delights?

Yet, for all its grandeur, the cathedral and its dome have not been as impervious to the elements and other outside forces as Agnolo suggests. Vasari was to claim that the heavens themselves are envious of the dome, since every day it is struck by lightning, and over the years a number of these strikes have caused serious damage. No means of countering lightning existed at the time, and a system of lightning rods was not introduced at the cathedral until the second half of the nineteenth century, by which time the lantern had needed major repairs on several occasions.
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The most dramatic of these blows fell on April 5, 1492, when a lightning bolt sent several tons of marble cascading into the streets on the north side of the cupola, in the direction of the Villa Careggi, which stands in the hills above Florence. The Villa Careggi was the country home of Lorenzo de’ Medici, the grandson of Cosimo de’ Medici and, like Cosimo, the ruler of Florence and a generous patron of the arts. To Lorenzo, lying ill with a fever in the villa, the meaning of the destructive strike was unmistakable: “I am a dead man!” he exclaimed upon being told in which direction the rubble had fallen. Lorenzo’s physicians attempted to avert this fate, feeding him potions made from pulverized diamonds and pearls, and cautioning him to avoid both grape pips and the air at sunset, two things considered fatal to a man in his condition. But they labored in vain, and true to his prediction Lorenzo died three days later, on Passion Sunday.

In 1639 a series of cracks appeared on the interior of the inner shell. These are similar to those that appeared at almost the same time in the dome of St. Peter’s. They run vertically from the oculus to the drum, cutting through Vasari’s fresco and in many places following the line of the herringbone bond. The causes of these fissures, as well as the remedial measures they call for, have been matters of debate ever since. Sophisticated thermal measuring devices have been inserted into a series of holes bored in the inner dome in order to monitor the cracks, and in 1970 Rowland Mainstone suggested as their probable cause the expansion of the iron rods in the iron-and-sandstone chains. This increase in size was the result, he claimed, of both temperature changes and the penetration of the masonry by moisture, which was causing the iron to rust. He found that the cracks were not, like those in the dome of St. Peter’s, the result of an inherent structural deficiency, given that the materials used were able to withstand the stresses generated by the cupola.
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Another cause might be the cathedral’s alarmingly poor foundations: in the 1970s a hydrologist discovered that a subterranean stream flows under the southwest corner of the dome, directly beneath the pier in whose staircase tourists now begin their ascent. The massive cupola was raised, in other words, on top of an underground river.

The lantern being struck by lightning in 1601, and the scaffolding erected to repair it.

Shortly after Mainstone’s analysis, a commission appointed by the Italian government reported, to widespread alarm, that the cracks in the dome were growing in both length and breadth. This claim had been dramatically illustrated a few months earlier by the fall of a large fragment of Vasari’s fresco. The worsening situation was blamed on a violent form of stress that Filippo, for all his genius, could not have anticipated: heavy traffic. Cars and buses were immediately banned from the area around the cathedral, and today only refuse lorries on their early-morning rounds are permitted to trundle through the Piazza del Duomo. Filippo’s dome, so long impervious to the harsh vagaries of the weather, is now also safe from the scourge of the motorcar.

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Today, as for the past five centuries, the mountainous form of the cupola dominates Florence. It looms above the narrow streets as you walk them, or breaks unexpectedly into view when you turn a corner or enter a piazza. It can be seen from the steps of churches such as San Miniato al Monte, from hotel balconies (as Lucy Honeychurch discovers in E.M. Forster’s
A Room with a View)
and from the terraces of cafés.