Dry Tortugas National Park in the Gulf of Mexico

Tony Arruza / CORBIS

Boondocks, USA
Located 70 miles from Key West in the Gulf of Mexico, Dry Tortugas National Park is a collection of seven tiny islands that can be reached only by boat or plane, making it the country's most remote national park. Besides a stunning amount of marine life (it's home to the third-largest barrier reef system outside of Australia and Belize), the park boasts an impressive military and nautical history. The 163-year-old stronghold of Fort Jefferson was once used to house prisoners during the Civil War, and a 17th-century Spanish galleon uncovered by divers in 1989.