Blowhard, Esq. writes:

Based on prehistoric building technique, dry-stone houses with conical roofs are found throughout the Mediterranean region and beyond. They follow similar construction principles, but each type has its own name and style. The trullo (pl. trulli) is the name for such building that are found scattered throughout the countryside of the Itria Valley of the Apulia region of southeast Italy. The trull guild in this region are either rectangular structures with truncated pyramid roofs or circular structures with ogival (pointed) roofs…The trulli here are distinctive rectangular-plan buildings, containing several square rooms with conical roofs, connected by semicircular arches.

These trulli are constructed out of roughly worked limestone boulders, collected from neighboring fields, and were built, without foundations, directly on the underlying natural rock, using the dry-stone technique (without mortar)…These walls are extremely thick, providing a cool environment in hot weather and insulating against the cold in the winter…

— Building Without Architects: A Global Guide to Everyday Architecture