Explore the Caribbean's U.S. National Parks

Two-thirds of the island of St. John is protected national park land, including 7,000 acres of forest, beaches, historic sites, and hiking trails. In fact, some of the finest beaches in the Caribbean are located in the park, including Trunk Bay with its famous underwater snorkeling trail and Cinnamon Bay, which has a campground just steps from the shore. The popular Reef Bay Trail leads to the ruins of a historic sugar mill before ending at a secluded beach where you can plunge in and cool off before your return hike.

The Virgin Islands Coral Reef National Monument, which protects coral reefs offshore of St. John (including the famous Hurricane Hole), is also administered by Virgin Islands National Park; rangers can provide visitor information.

El Yunque is as unique as it is popular -- the only tropical rainforest among the U.S. national forests and a destination for legions of visitors to Puerto Rico. Most visitors here on daytrips see only a fraction of the park, perhaps making a stop at the El Portal Tropical Forest Center or hiking to the El Mina waterfall, but the park has 24 miles of trails to explore, including hikes to the top of El Yunque Peak and the Mt. Britton Lookout Tower.

This national park (and World Heritage Site) in Old San Juan preserves the remarkable fortifications built by the Spanish to protect their prized Puerto Rico port from attack by the British, French and other Caribbean rivals. The park includes the most iconic buildings in this ancient walled city (including the walls themselves), such as the Castillo San Felipe del Morro ("El Morro"), Castillo San Cristobal, the San Juan Gate and, across San Juan Bay, the Fort San Juan de la Cruz.

 There are few places left where you can legitimately feel like you've stepped back in the past a few centuries, but this historic park in the capital of St. Croix, U.S. Virgin Islands, is one. Preserving a cluster of 18th- and 19th-century buildings on the Christiansted waterfront, the park speaks to a time where this was a key Danish trading post in the Caribbean. The park includes five key structures: Fort Christiansvaern (1738), the Danish West India & Guinea Company Warehouse (1749), the Steeple Building (1753), the Danish Custom House (1844), and the Scale House (1856).

 Just offshore of St. Croix is one of the Caribbean's best protected and healthiest coral reefs, which visitors can explore via snorkel tours that also include a stop on Buck Island itself for some beach time, picnicking, and perhaps a hike to the peak for a panoramic view of St. Croix and the Caribbean Sea.

Infrequently visited and only marginally accessible, the Salt River Bay National Historic Park and Ecological Preserve on St. Croix includes the remains of the oldest European fort in North America and the spot where Christopher Columbus had one of his many fatal encounters with local native tribes. The best way to visit Salt River Bay is via a kayak tour, which can be arranged with local outfitters.

We like to think of the Florida Keys as the American Caribbean, and one of the must-do's when visiting Key West is taking a ferry ride out to Dry Tortugas National Park. Much like Buck Island, this 100-square-mile park is mostly underwater, protecting precious coral reefs and seven small islands. On land, the highlight is visiting Fort Jefferson, a massive 19th-century masonry fort on Garden Key, and sunning yourself on the islands' many sandy beaches.

The quiet island of Culebra, off the east coast of Puerto Rico near Vieques, is surrounded by smaller islands that comprise -- along with a Mount Resaca and several virgin stretches of shoreline on the bigger island -- the Culebra National Wildlife Refuge. More than 50,000 seabirds make the refuge their home, and visitors can enjoy hiking trails and deserted Caribbean beaches.