Alligator Rivers is the name of an area in the Arnhem Land region of the Northern Territory of Australia, containing three rivers, the East, West, and South Alligator Rivers. It is regarded as one of the richest biological regions in Australia, with part of the region in the Kakadu National Park. It is an Important Bird Area (IBA), lying to the east of the Adelaide and Mary River Floodplains IBA. It also contains mineral deposits, especially uranium, and the Ranger Uranium Mine is located there. The area is also rich in Australian Aboriginal art, with 1500 sites. The Kakadu National Park is one of the few World Heritage sites on the list because of both its natural and human heritage values. They were explored by Lieutenant Phillip Parker King in 1820, who named them in the mistaken belief that the crocodiles in the estuaries were alligators.