Sihanoukville, Cambodia

Sihanoukville sits on the lovely island-studded Bay of Thailand. Neighboring the city is the ecological gem Ream National Park, an 81-square-mile reserve that encompasses a variety of land and marine habitats including evergreen mountain forests, mangrove forests, reefs and freshwater wetlands. There, you might see dolphins, dugongs (a type of manatee) or monkeys. Beach lovers will want to soak up the sun on tree-lined Serendipity Beach, with fine sand and clear water.