Aldabra Atoll, situated 1,150 kilometres south-west of Mahé, is the largest raised coral atoll in the world, comprising more than a dozen islands bordering a lagoon so vast the whole of Mahé could fit inside its perimeter. Aldabra’s exceptional and pristine condition has earned it the distinction of being named a UNESCO World Heritage Site, one of two such sites in Seychelles. The atoll’s islands nurture a vast array of both unique flora and fauna as well as the world’s largest population of 150,000 giant tortoises, and its lagoon boasts the most vibrant marine life of the entire archipelago. First given its name by Arab seafarers, the atoll’s harsh, sun-baked environment and the fast-flowing waters of its lagoon typically kept all but the most intrepid explorers at bay. But there has been a tiny permanent settlement on the island since 1874, made up chiefly of contract labourers from Mahé engaged at different times in fishing, mining guano and producing coprah for sale on the mainland. The Seychelles Island Foundation (SIF) now supervises the island and strict regulations governing the island’s accessibility are in force to protect its fragile ecosystem. A small research station affords accredited scientists the opportunity to study the atoll's biodiversity, but there is no hotel accommodation on the island. Yacht charters are available, however.