The Cát Bà Archipelago in northern Vietnam is made up of 367 islands that span 100 square miles (260 sq. km) in the southeastern edge of Lan Ha Bay. The largest island — also called Cát Bà — has roughly 13,000 inhabitants, with an additional 4,000 people living on floating fishing villages off the coast as seen here. The island is the adventure-tourism capital of Vietnam, with places to mountain bike, rock climb, hike, and more.