On a sweltering July afternoon near Ostuni, 19-year-old Giuseppe Fragnelli hammered a limestone slab into shape on a trullo roof, pausing at 12:30 p.m. as regional orders require — a reminder that even the ancient builders knew when to call it quits in the worst heat. Step inside that same trullo, though, and you'll find something remarkable: a natural chill that can make the difference between unbearable and bearable feel like night and day.
"There are between 7 and 10 degrees (centigrade) difference between inside and outside a standard trullo. But sometimes there can even be a 15-degree difference," said Francesco Fragnelli, a trulli restorer who learned the craft from his cousin in 1983 and now works alongside his brother and nephew. The secret lies in walls that measure between 1.5 and 3 meters thick, built from roughly worked limestone boulders that farmers collected as they cleared fields over centuries. The stone absorbs winter moisture and slowly releases it during summer, while hot air rises through the conical roof, pulling cool air down below.
Once symbols of a hard-knock life — built as simple shelters and storehouses from the mid-14th century — the gray-and-white trulli of Puglia had fallen into deep disfavor by the 1980s. "Cement was in fashion. The trulli represented a past age, one of suffering and hunger," Fragnelli told AFP. But as Italy's summers grow longer and more brutal, these centuries-old structures are commanding renewed attention.
Gerardo Biancofiore, who leads the Puglia branch of the national builders association ANCE, told AFP that demand for trulli has risen sharply in recent years and shows no sign of slowing. He worries, however, that some modern builders are using "skills, techniques and materials incompatible with dry stone buildings," and is calling for formal training schemes to preserve authentic restoration methods for a new generation of craftspeople.
In Alberobello — a UNESCO World Heritage town where hundreds of trulli cluster across the hillside — the structures have found new life as boutique homes, restaurants, and shops. Chef Domenico Laera operates one such restaurant without a single air conditioning unit. "The temperature is naturally cool for eating," he told AFP, calling the experience "magical."
Biancofiore points to the trullo as a model for what architects call bioclimatic design — buildings that work with climate rather than against it. "With the increase in heat waves, traditional solutions are becoming a valuable reference, capable of inspiring climate adaptation strategies for contemporary construction as well," he said. As scientists warn that extreme heat events will only grow more frequent across southern Europe, these ancient stone cones are being studied not as relics, but as blueprints.