Aldabra is the world's second largest coral atoll (21 x 9 miles) and the world’s largest raised coral atoll (elevation of 26 feet). Located in the Outer Islands of the Seychelles, Aldabra’s four islets surround a large shallow lagoon encircled by coral reef. These channels make for spectacular drift dives into the lagoon. Aldabra is a habitat for the coconut crab (world’s biggest crab) and is a breeding ground for green and hawksbill turtles. Aldabra is also home to the world’s largest population of giant tortoises as well as the Aldabra rail, the only surviving flightless bird species of its kind. We visited this World Heritage Site in 2002.