R. A. Scotti

by Basilica: The Splendor;the Scandal: Building St. Peter's

  Sixtus was sixty-five when he became pope, not a felicitous man in spite of his name, but intrepid. His rough edges were on display. He was uncouth, blunt, and even more impatient than Julius. His health was poor from years of poverty. He had much to accomplish, and he knew that time was not on his side.

  Generally considered the father of modern Rome, Sixtus was the last of the great reforming popes of the Counter-Reformation and the last in the lineage of iron-willed old men, without time or patience, who pushed St. Peter’s toward completion.

  CHAPTER TWENTY-FIVE

  RAISING THE DOME

  Amonastic quietude pervades the Basilica of St. Paul’s Outside the Walls. It is a soothing sanctuary apart from the rush of the city. In June 1588, morning just breaking and the even cadence of monks chanting the matins seeping from the distant recesses of the choir, Giacomo della Porta and his assistant Domenico Fontana spread a huge drawing on the pavement.

  Della Porta had been the chief architect of St. Peter’s for a dozen years when Sixtus V became pope. He had started as a sculptor under Michelangelo, shaping stucco reliefs, and had built in his teacher’s shadow. Michelangelo had taken on a number of major projects during his final years, and della Porta became the cleanup man, faithfully executing the master’s designs for Palazzo Farnese, the Campidoglio, and now the Basilica of St. Peter.

  According to the records in the Fabbrica archives, on the recommendation of Michelangelo’s friend Tommaso de’ Cavalieri, della Porta was named architect of St. Peter’s on May 12, 1574. The Basilica progressed rapidly under his direction. Della Porta tore down the old Rossellino-Bramante tribune and rebuilt the west apse to conform to the other arms. He completed the large northeast corner chapel, called the Chapel of St. Gregory for Pope Gregory XIII, and raised the first of the minor domes over it. Then he broke ground for a corresponding chapel in the southeast corner. In June of 1584, the Fabbrica reported, “The Church of St. Peter is growing on every side.”

  By 1588, della Porta had successfully completed more of the Basilica than any single architect, and he had never deviated substantially from his teacher. But on this June morning, he was proposing an extraordinary exception—a new Basilica dome, radically different from both Michelangelo’s and Bramante’s.

  When he died, Michelangelo “left his soul to God, his body to the earth, and his goods to his nearest relatives.” Those goods included more than eight thousand ducats tied up in handkerchiefs and small bags and stashed in various places—a polished walnut box, a copper vase, and a majolica jug—as well as a variety of household items, including an iron bed with a white linen canopy, a kidskin blanket, and an assortment of linen and clothing. But his true last will and testament was the fifteen-foot scale model of the dome of St. Peter’s, fashioned from limewood on a ratio of 1:15. Michelangelo had built the large model in his final years so that, in the event of his death, the Basilica dome would be completed exactly as he had intended.

  Every pope since Paul III had sworn a solemn vow to continue Michelangelo’s work precisely as he had ordained even after his death. Awed by his talent, intimidated by his genius, and bound by their promise, the popes became paralyzed. How do you follow genius? No one had been able to build the dome to Michelangelo’s precise specifications or dared to suggest another plan. Twenty-two years later, the Basilica drum still loomed over the city like a headless giant—overgrown, neglected, moss and wildflowers sprouting in the window frames.

  Michelangelo was a legend in life, and in death he had become one of the immortals. If artists were canonized for their talent, he would be seated at the right hand of God. Della Porta was an experienced, competent architect. He did not pretend to have the gift of his teacher, yet he had not simply modified Michelangelo’s dome, he had redrawn it.

  Now he and Fontana were laying a huge paper cutout of the new dome on the sanctuary floor of St. Paul’s. The large open space was removed from the distractions of the city, and looking down from the adjoining choir at the cutout spread on the pavement, a layman like Sixtus V could picture the cupola clearly.

  Della Porta was not easy with this new pope. The architect was a genial, easygoing man of ample appetites. He liked the good life—good food, good wine, good company, all in abundance. Sixtus was a fierce taskmaster, driven and driving. He had no patience with jobs unfinished or problems unsolved, and he wanted to see Michelangelo’s dome rising triumphantly. In his determination to complete the Basilica, he had made the Fabbrica a congregation within his reformed Curia, renamed it somewhat grandly La Congregazione della Reverenda Fabbrica di San Pietro, and given it the means, the authority, and the money to get the job done.

  Now, framed in the arch of the choir with the cardinal administrators of the newly organized congregation pressed around him, Sixtus appeared like a white staccato note in a field of red. Pushing the others aside, he leaned over the rail for a closer look.

  For the entire century, ever since Bramante had drawn his first smooth saucer shape, the dome had posed a challenge: Could it be built? Could the piers bear its weight—even strengthened and reinforced several times so that now they were 240 feet in circumference, eight feet thicker than Bramante had made them?

  Della Porta’s reasons for altering the dome were practical, but even with his changes, the challenge was enormous, and success was not foreordained. In the ambivalence of a summer morning, he waited nervously for the pope’s reaction, bowing humbly one moment, then straining the next to read the expression that clouded the papal countenance. Della Porta anticipated many questions from the former grand inquisitor. He expected the pope to consider the design over several weeks and confer with his cardinals, but Sixtus was as decisive in this as he was in all things. He asked only one question: How long will it take?

  There was no way to predict with certitude. The last time an undertaking of such magnitude was attempted in Rome had been 1,450 years before, in the reign of the emperor Hadrian, when the dome of the Pantheon was raised.

  How long will it take if all goes well, with God’s help and no complications? Della Porta estimated ten years. Sixtus allowed him thirty months, and promised all the money and men he needed.

  The architect must have tried to protest. Or he may have been so stunned that all thoughts and words emptied from his mind, and he stood speechless, staring at his own bold drawing. He could not deny or contradict the pope, and there was no common ground between them. He must have wanted to throw up his hands and curse such a ridiculous decree. Ten years, and he was being optimistic, a courtesy because the pope was an old man and dogged in his insistence on seeing the dome in his lifetime.

  Rome was not built in a day, and neither was its church. It had taken Bramante seven years to set the piers, and then they had to be strengthened twice. It had taken Michelangelo seventeen years to build the drum, and now the pope was giving him, Giacomo della Porta, a mere mortal, not a genius, not divinely gifted, thirty months. It was a scherzo malevolo, “a black joke.”

  Della Porta must have appealed to Fontana to point out, with humility, the utter, utopian madness of imposing such a timetable. Fontana was one of the few in the Vatican who enjoyed an easy relationship with the pope, and he knew better than to argue. Sixtus was in failing health. Death was more than a shadow. It was a proximate reality. He was determined to restore the city, and even more determined to see the dome of St. Peter’s raised in his lifetime.

  In the summer of 1588, as the Spanish Armada sailed toward Britain to regain England for the Church, della Porta began to raise the cupola. The construction yard in front of the Basilica teemed with masons, stonecutters, bricklayers, cement mixers—as many as eight hundred laborers. There were no siestas, no dinner breaks. The work was continuous night and day, every day, with only an hour of quiet for Sunday mass. In the wicked heat of the Roman summer, bolts of sun-bleached canvas stretched across the building site. The stench of manure from the mules and oxen that lugged the wagons, the rumble of the carts, the shouted orders
, the belch of the forges, were ceaseless, and nights seemed louder than days because the din of the city quieted.

  Bramante had analyzed the techniques of the ancient Roman architects. Michelangelo had sent to Florence for the measurements of Filippo Brunelleschi’s cathedral dome. But each step in the construction was an experiment—a process based on a mix of imagination, guesswork, intelligence, and experience.

  Over time, every aspect of the dome—its slope, contour, rise, and angle of elevation—had changed. Bramante’s shallow hemisphere was a horizontal, saucer-shaped dome—a single shell of cemented masonry on the model of the Pantheon’s. Antonio da Sangallo’s dome was a tiered wedding cake. Michelangelo’s rounded dome brought elements of Brunelleschi’s Duomo in Florence to Bramante’s Pantheon.

  One of the most impressive constructions of the Renaissance, Brunelleschi’s dome had taken sixteen years and enormous ingenuity to raise. It was the only model on a scale comparable to the Basilica dome, and Michelangelo borrowed several elements from it—the two shells, the ribbed construction, and the windows in the drum and cupola.

  Double shells offered the advantages of a protective shield against the weather and a heightened, more visible profile. Della Porta’s dome was also double skinned, but far bolder. While his inner shell retained Michelangelo’s rounded contour, the outer shell that fills the sky over Rome diverged radically. Separating from the interior skin, it rises at a steep angle, changing the emphasis from a disk to an ellipse.

  Della Porta’s concerns were not purely, or even primarily, aesthetic. He believed that the higher, more pointed shape would disperse the weight and lessen the lateral thrust. Later science would support his theory. An elliptical arch generates as much as 50 percent less radial thrust than a hemispherical arch.

  Physics was in its infancy, and as late as the sixteenth century, architects and engineers did not understand the science of statics and equilibrium—the engineering principles underlying the design of a stable structure. They knew, for instance, that walls had to have a certain thickness proportional to their height, but not the precise ratio of one to the other. The most basic analyses—how to determine the stability of a site or measure the thrust of an arch—were conjecture.

  In essence, a dome is a series of arches, and conventional wisdom held that the semicircular Roman arch directed the thrust down into the piers, abutments, and foundation base. Architects knew that an arch exerted a thrust that had to be either balanced by another arch or absorbed, and that the mechanics of a dome are similar to those of a barrel. Both have a natural tendency, called hoop tension, to burst out. Still, calculations were often erroneous.

  An architect like Bramante, constructing a monumental edifice on the scale of St. Peter’s, had very little true understanding of the forces of physics involved—stress and strain, action and reaction, statics and tension. The surprise is not that the bell tower of Pisa listed or that the Gothic cathedral of Beauvais collapsed but that so many marvelous buildings have stood for so long. The principles of stable construction were not understood clearly until Galileo formulated the laws of mechanics and applied them to architecture.

  Raising a dome of such monumental scale was an experiment never before attempted. The base of the drum began ten feet above the height of the oculus of the Pantheon, and if its construction were accomplished, the dome of St. Peter’s would be the equivalent of a ten-story building placed on top of Brunelleschi’s dome.

  As the vaulting rose over the Basilica, how many times in the long nights of construction must della Porta and his masons have woken up in a cold sweat? Were the foundations deep enough? Would the drum hold the massive weight? Should they diminish the thrust of the cupola? Many prayers must have been offered and fervent promises made to God, to the Blessed Mother, and to St. Peter at each step in the precarious construction.

  Michelangelo had intended the pilasters of the drum and the ribs of the cupola to act as buttressing forces. But by increasing the angle of elevation so radically, della Porta reduced those elements to little more than ornamentation. His heightened cupola is an almost perfect catenary curve. All its parts should support one another by their own weight, allowing it to hang freely between its two points of support in perfect equilibrium.

  Della Porta formed the shells almost entirely of heavy masonry laid in a herringbone pattern. Frequently used by the architects of ancient Rome, the method of fitting bricks together in an inverted V design applies pressure equally from both sides, preventing hoop tension. The two shells spring from the attic as a single form for almost twenty-eight feet before they begin to diverge. As they separate, the space between them forms a third element that affords both ventilation and access. Sixteen ribs, corresponding to the sets of pilaster-framed windows in the drum, start at the point of departure. They divide the cupola into sections, creating a frame or skeleton. Carved at the base of each rib are three mountains, the symbol on Sixtus’s papal crest. The ribs are uniform in width and extend through both shells, curving inward and tapering as they ascend, gradually increasing in depth as the distance between the shells widens, until the thickness is almost double.

  Three rows of small eye-windows pierce each section, bringing more light into the interior dome and illuminating the vaulting. A team of masons worked on each section, constructing the shells simultaneously. The two skins begin as a solid, almost ten feet thick. At a height of just under twenty-eight feet, they start to separate, diverging gradually until there are ten feet between them at the apex.

  To support the enormous weight and further counteract the outward thrust, three iron rings were forged in the Vatican foundry and fitted within the masonry—two in the solid mass of bricks where the curve begins, and the third midway to the apex. Like the iron bands around a wine barrel, the rings around the majestic dome of St. Peter’s contain its tension. The larger iron rings weigh more than 18,000 pounds each, the smaller ones more than 16,500.*

  By Christmas, the cupola was more than forty feet high and still rising. Romans were astonished. The oldest had lived their entire lives with the unfinished Basilica silhouetted against the western sky. It had become a dream with no reality. Children had grown up, had children of their own, and grown old, and still the Basilica stood unfinished. Now, all of Rome watched with mounting excitement and unconcealed wonder as the vista changed. Waking up each morning, they scanned the skyline. Sixtus watched with the rest of the city and received regular progress reports. As long as the dome was proceeding, he didn’t meddle.

  In the rush to meet the pope’s schedule, della Porta pressed forward in fair weather and foul. His men labored through the summer, working at heights of more than two hundred feet, exposed to the broiling sun. Ingenious time-saving measures were sometimes called for. Once when an extra container was needed for water, a mason commandeered the sarcophagus of Innocent VI and used it as a trough. Rather than waste time descending and ascending again, the workmen took their midday meal high in the air, and some days were so hot that the cheese in their meal bags melted on the bread and the wine mulled in their kidskin flasks.

  In autumn, they huddled in the passageways within the walls of the drum and waited out the rains that come in sudden, short drenchings in Rome, then went back to work. When lightning flashed, it seemed close enough to singe their beards, and when winter blustered in, the wind at such a height was a slashing knife. Scaffold castles rocked, and the men hung on, fingers stiff and blue, and in the blue distance they looked out on the Sabine mountains, and beyond to the campagna, the Alban Hills, and the sweet vineyards of Frascati. They looked out so as not to look down.

  The men and stone and furnaces below were blurred spots before their eyes, and they tried not to remember the iron band that had snapped on a scaffold, setting in motion a fatal chain of cause and effect—the scaffold castle tilting, one triangular leg slipping off the attic, and a mason dangling over the vast construction, his mouth wide open, the wind swallowing his voice. He floated over the Basi
lica, caught on a thermal, before tumbling in free fall, gathering speed. Against all odds, the men kept climbing the infinite height each day, and each month the cupola rose another seven feet.

  Conceived in the fall of 1505, the dome of St. Peter’s was completed eighty-five years later. Such a magnificent architectural achievement would seem to require calm deliberation and slow, careful construction. But the dome was raised in a hurry—or more precisely, in several intense, often incautious bursts of feverish work by old men racing against their own mortality—Bramante setting the foundation piers that made the Basilica his own, Michelangelo approaching his eighty-ninth year and staving off death to assure that his dome would crown the mother church, Sixtus V holding his architects to a frenzied schedule, twenty-four hours a day seven days a week, only allowing a break for Sunday mass.

  Finally, on May 14, 1590, as the Basilica choir sang the Te Deum and Sixtus gave thanksgiving, the final stone, carved with his name, was set. A week later, on May 21, the indomitable pontiff issued a formal announcement: “To the perpetual glory of His Blessedness and the discomfiture of his predecessors, Our Holy Father Pope Sixtus V has completed the vaulting of the cupola.”

  The dome of St. Peter’s was raised at last, not to the design of Bramante or Michelangelo but to the specifications of the unsung hero of the Basilica story, Giacomo della Porta.

  In architectural renderings, Bramante’s hemisphere feels earthbound, flattened over a vast diameter. Michelangelo’s globe seems aspiring, as if it is reaching toward heaven, recalling the hope of salvation. Della Porta’s dome seems not to rise from below but to be suspended from on high, brick and mortar and iron rings freed from the gravity that holds us earthbound. Visible from every point in the city, his dome is inescapable. It is the symbol of both the city and the Church of Rome, dominating the Roman skyline and proclaiming the faith: Cristos aristos.