Le Sirenuse, in Positano, on the Amalfi Coast, is the rare world-class property that manages to be at once patrician and utterly un-stuffy. Maybe it feels like a home because it was one—the original villa has been in the Sersale family for centuries. The Piranesi etchings and museum-quality antiques in the former chapel are family heirlooms, and the black-and-white photos in the spa chronicle the owner’s lifelong wanderlust. –P. G.