Decades ago, I lived in an apartment only a few minutes’ walk from St. Peter’s Basilica in Rome. I have never loved the huge basilica, nor the triumphalism it proclaims with such confidence. At the same time, the city is impossible to imagine without this monument to the center of Catholic Christendom and to the genius of its builders, chief among them Michelangelo Buonarroti. The dome casts a long shadow over Rome, both literally and metaphorically. It dominates the horizon like nothing else, a colossal declaration of humankind’s capacity to overcome the impossible, to create an architecture of wonder.
Engineer Wayne Kalayjian’s book Saving Michelangelo’s Dome: How Three Mathematicians and a Pope Sparked an Architectural Revolution (2024) describes a little-known but crucial crisis in the history of the Cupolone, or the “big dome,” as the Romans simply call it, in contrast with the many smaller domes dotting the city skyline. This crisis was as baffling as it was disturbing. The dome was finished in 1590 and its lantern, the structure atop its peak, was completed three years later.
However, by 1740, a series of cracks riddled the dome, probably due to the weight of the lantern, and they were getting bigger. Kalayjian buries the lede, though, leaving until near the end of his book the urgent and alarming notice that a 2019 study found that “the static conditions of the dome [in 1740] were actually quite critical [and the dome was] even close to failure.” Architects at the time were, on the whole, overconfident that Michelangelo’s celebrated genius had taken every factor into account, never mind that he had died in 1564 having only completed the cylindrical parts of the dome, the attic and the drum, nor that his plans for a hemispherical dome would have doomed the Cupolone upon its construction with an intolerable outward thrust. A far less famous architect, Giacomo della Porta, redesigned the dome with a taller section, saving Michelangelo’s reputation. But he built it with undue haste in only two years at the urging of then-Pope Sixtus V, who lived just long enough to see it completed.
The author introduces us to the main characters in the story with efficacy. Since the general reader may not know much about 18th-century Rome, this is both necessary and welcome, and Kalayjian takes as his hero Pope Benedict XIV Lambertini (1740–58), an open-minded, modest, and humorous man who gave Rome its first two public art collections, both gifts to the city itself and not to the papacy, which we now know as the Capitoline Museums and Picture Gallery. Kalayjian paints a vivid picture of the other principals in the story: the stolid but successful papal architect Luigi Vanvitelli and the masterful engineer and scaffold-builder Nicola Zabaglia, arguably the secret genius behind the whole enterprise. The principal mathematician was the extraordinary intellectual Giovanni Poleni, who devised a series of five heavy interlocking iron chains to be built into the drum and dome. This is a story worth telling, and these are people worth resurrecting in print.
Less successful is Kalayjian’s attempt to extrapolate from the rescue work on the dome a bigger picture of the invention of modern engineering. In the end, this ambitious goal gets short shrift with a brief chapter before the epilogue. This is where the “three mathematicians” of the book’s subtitle come in. The French Thomas Le Seur and François Jacquier and Balkan-Venetian Roger Boscovich collaborated on a study based on mathematics that they applied concretely to the problem of the dome and its cracks. Naysayers at the papal court sidelined these mathematicians and they all ended up working in France. Although their theories about the dome of St. Peter’s were right, they are at most a footnote in the story, and while they were arguably more important to the developing European Enlightenment, they feel shoehorned into the book’s narrative.
Though the author makes various small errors, displaying a superficial knowledge of this historical period, they are never ones of interpretation. He is absolutely right to underline the astonishing brilliance of his protagonists and their solutions, and to place Benedict XIV’s Rome at the heart of a burgeoning movement of scientific inquiry that soon spread across Europe. In the mid-18th century, it was still possible to reconcile Catholic faith with the study of science, though after Benedict’s death the Church retreated from the threatening intellectual freedoms of the Enlightenment and back toward its own authority. But he lived long enough to see Michelangelo’s dome saved by science, mathematics, and engineering, and Kalayjian does us a service in reminding us of that.
Saving Michelangelo’s Dome: How Three Mathematicians and a Pope Sparked an Architectural Revolution (2024) by Wayne Kalayjian is published by Pegasus Books and available online and at independent booksellers.
