Rising from a boulder-studded hillside on the Puerto Rican island of Vieques is a cluster of concrete buildings that look deceptively like bunkers. In fact, Hix Island House, the vision of Toronto-based architect John Hix, is an unusually fashionable member of the Caribbean's roster of eco-hotels. Informed by a Zen aesthetic, Hix's 12 minimal apartments in three (one brand-new) solar-powered casas are notable for their glass-free windows, unfinished wooden shutters, and heavy metal doors- a formula that has so far been hurricane-proof. Interiors incorporate poured-concrete bed platforms and banquettes, rustic blankets, and Hix's own plywood chairs, inspired by de Stijl designer Gerrit Rietveld. Hix has also added a stunning pool and a yoga studio. But if you're not into sun salutations, contemplating the Caribbean from the deck of your Island House pad might prove enlightening enough. Pilón Area, Vieques; 787/741-2302;; doubles from $170, including breakfast.