Tuscany has been on the map as a recognizable cultural entity for almost three thousand years, but it's hard to say how much of the Tuscan sense of life really harks back to antiquity. Ancient Etruria, a federation of Etruscan city-states, was folded into the Roman Empire in the third century B.C., creating the fundamental mix, and it's arguable that something in the ancestral identity never wholly disappeared—one thinks of the olive tree and the cypress, of travertine construction, of certain habits of speech—and in the later Middle Ages roughly the same entity was reunified under Florentine rule. Florence's power grew out of the wool trade, banking, and the acquisition of Pisa and Siena; her great prestige in the arts and sciences lasted roughly from 1300 to 1550. The Medici, a banking family that came to dominate the city, managed to get itself ennobled in the mid-sixteenth century and governed Tuscany as a grand duchy until the reunification of Italy in 1861. But Tuscany has changed greatly over the centuries, and even the townsfolk of closely linked cities such as Pisa and Livorno are given to merrily disparaging one another.

One feels, all the same, that certain people, ideas, and monuments produced by this land could not possibly have been produced anywhere else. It belongs to the genius of the Italian city to possess some emblematic attraction that enchants and amazes visitors, like the Palio, Vesuvius, or the Grand Canal, and Pisa has the greatest of them all, the Leaning Tower. More than any other symbol, this one also memorializes an abiding aspect of the Tuscan genius: the spirit of mathematical inquiry and its happy conjunction with the art of design. When I arrived in the city last spring, I made my way straight to the aptly named Piazza dei Miracoli—home of the tower, the duomo, the baptistry, and the camposanto, or cemetery. Pisa has preserved all the attributes of a small European university town—the bookshops, the crowded cafés, the flocks of students on bicycles—and as I hurried toward my destination, relishing this stream of life pursuing its traditional path, I almost forgot to look ahead. All at once, floating over the roofline of the Piazza Arcivescovado, slanting improbably into the heavens like a storybook Tower of Babel, ringed by the most delicate rows of white arches imaginable, was the greatest architectural delight the world has to offer.

Virtually all Renaissance church towers are pierced with progressively more windows as they rise, to lighten the load, but this one soars upward in the form of an almost unperforated cylinder. Defying gravity, it looks weightless, a miraculous column; any monotony in the design is mitigated by the rings of white arches. And yet it leans, and it started to lean—because of subsidence—by the time the builders reached the third story: It was, to the permanent astonishment of architectural historians, built leaning. In that sense, although it defies gravity, it becomes, paradoxically, evidence for gravity and a sort of popular sign of the earth's gravitational field. Like human beings, who have something angelic about them but who often behave like animals, it delicately conjoins two opposing qualities. I believe it is for this reason that Galileo's disciple Vicenzio Viviani, in his biography of his master, had the great Pisan physicist prove the law of fall by dropping weights off the Leaning Tower. We know that he didn't do it, not like that and not here; but here, poetically, is where we feel it had to happen.