Although the islands of Vieques and Culebra (known as the "Spanish Virgins") are only a few miles off the coast of Puerto Rico, they feel like another world. While the mainland rings with the adrenaline rush of Latin America, this pair of palm-fringed islands has the laid-back vibe of the Caribbean—indeed, St. Thomas and St. Croix are clearly visible from the eastern edges of Culebra.

Vieques and Culebra are alike in many ways. Neither has much traffic—in fact, you won't find a single traffic light on either island; high-rise hotels haven't cast a shadow on the beaches; and there are no casinos, fast-food chains, strip malls, or most other trappings of modern life. "Barefoot" is often part of the dress code at casual restaurants, and the hum you hear in your room is more likely to come from a ceiling fan than an air conditioner. Things happen here poco a poco: slowly, at an islander's easy pace.

Beautiful beaches abound on both islands. Many of the best stretches of sand on Vieques—Chiva, Caracas, and Punta Arenas, to name a few—are on land that was once part of a U.S. naval base. This means that resort development hasn't reared its ugly head. It also means there are few, if any, amenities, so bring plenty of water and a picnic lunch. Most accommodations provide guests with beach chairs, towels, and coolers for the day; some will even pack guests' lunches to take to the beach. The beaches on Culebra are just as unspoiled; marine turtles are perfectly comfortable coming ashore to lay eggs.

Wild horses roam Vieques, where two-thirds of the island is a wildlife refuge protecting coastal lagoons, mangrove wetlands, subtropical dry forest, and islands—ecotourism is a key draw. Fishing in the turquoise flats just offshore is fantastic. And the island seems tailor-made for exploring by bicycle and/or kayak. Off Culebra, several cays delight birders with their colonies of boobies and other seabirds.

Some of the best snorkeling and diving in the Caribbean can be found in the waters surrounding Vieques and Culebra. You can sign up for a half- or full-day excursion to nearby coral reefs that teem with colorful fish. It's also possible to grab a mask and snorkel and simply wade out a few yards to see what you can see. Playa Esperanza, on the southern coast of Vieques, is a good place for beginners. More experienced snorkelers will prefer La Chiva (Blue Beach) or Punta Arenas (Green Beach).