The U.S. Virgin Islands is a triple threat: three isles, three styles, all accessible to U.S. citizens without cracking open a passport. St. Thomas is the most developed and easily accessible of the sunny trio, with regular flights from all over the U.S. It's a beach-lover's dream — strands run the gamut from tiny coves tucked into the scalloped coastline to Magens Bay, one of the most beautiful in the world. St. John is accessible only by ferry from St. Thomas and is two-thirds national park, with winding trails leading through marine forests populated with wild burros and dazzling lookouts (some topped by stone ruins) over quiet beaches.