Rock Islands Southern Lagoon, Palau

This gorgeous lagoon counts 445 uninhabited limestone, volcanic-origin islands, some in the shape of mushrooms, over 247,000 acres. It represents the world’s greatest collection of marine lakes (seawater lakes separated from the ocean)—and also boasts a reef system with more than 385 species of coral. Human traces stretch back more than 3,000 years, including 17th- and 18th-century stoneworking villages abandoned due to climate change and population pressure on the fragile ecosystem.