People have described Puglia as the new Tuscany, but the more time I spend here the more this description smacks of rather disingenuous marketing. Yes, there are hill towns and olive trees, but in every way it has a rougher, wilder, and more arid beauty, less contained and, for some, less digestible. Part of the charm of Tuscany is how its insular way of life has been relatively undisturbed since the Renaissance. Here in Puglia, I feel like I've stumbled into a place much more multifaceted in its makeup, where the interplay of different cultures over the centuries produced a markedly separate identity.

My thoughts are suddenly underscored when Ostuni—known as the White City for its whitewashed buildings jutting against the sky—appears in front of me. How can Tuscan architecture be compared to this? Established as a Greco-Roman settlement in the first century a.d., the town is spread over three hills, with spectacular views of the plains and the sea. I while away a few hours in the maze of cobblestoned streets, enjoying the midafternoon solitude. The place seems transplanted from Greece, with the occasional Baroque detail thrown in, such as an ornamented eighteenth-century obelisk in the main square.

By the time I sit down for dinner in one of the town's oldest restaurants, Osteria Piazzetta Cattedrale, people have begun to reemerge from their cool homes and the atmosphere turns festive. Ostuni is known for having the area's most active nightlife, and by ten o'clock residents of every age have taken to the piazzas and bars, spilling out to fill the tables that abut the cathedral's bell tower. I sit on a daybed outside the fashionable Gipas III and people-watch with great satisfaction. When I leave at midnight, there's not a parking space to be had.

Frederick II, who ruled the region from 1220 to 1250, is perhaps the man most responsible for the way Puglia looks today. Due to the intricacies of medieval dynastic politics, the extraordinary Sicilian-born prince was named king of the Germans at his birth and was ruling over the Holy Roman Empire by the age of twenty-six. Known as Stupor Mundi (Wonder of the World), he controversially avoided the power center of Germany, preferring to spend most of his rule in southern Italy. Clearly Puglia was the favorite of his dominions, and it was here that he constructed sixty-nine castles and forty-two cathedrals. His architectural and cultural impact on the region was so great that wherever I go in Puglia, I feel as though I am retracing his footsteps.

And thus, under a scorching sun, I find myself panting my way to the base of the famously mysterious Castel del Monte. Sun-bleached, massive, and foreboding, it commands an imposing position on a remote hilltop overlooking the vast Murge Plateau. The castle is made more unusual by a repetitive octagonal shape—the eight sides of the structure mirrored in the eight rooms, the eight towers enclosing an empty octagonal courtyard. With only one small entrance, no moat, and a lack of space for soldiers and servants, the place is totally impractical as a fortress or even a country estate. Why Frederick chose to erect such an elaborate and isolated structure remains the subject of conjecture, and its mathematical precision and astronomical references have inspired generations of Da Vinci Code–esque investigators to search for hidden meanings. Like Stonehenge and the Mayan temples, it conjures a stirring reverence. I can't help but think that this was precisely the effect Frederick was after. From this elevated position, I can see even more clearly that the region's life is always drawn to the sea. Towns and sprawl hug the coast, while toward the interior, miles of trees, abandoned buildings, and the occasional farm are left untrammeled. I drive back along the roads that skirt these empty habitations and barely see another car.