 The shallow water reefs that can be seen in air-photographs and satellite images cover an area of 20,679 km2, most (about 80%) of which has grown on top of limestone platforms that are relics of past (Pleistocene) phases of reef growth.The remains of an ancient barrier reef similar to the Great Barrier Reef can be found in The Kimberley, Western Australia.The Great Barrier Reef World Heritage Area has been divided into 70 bioregions, of which 30 are reef bioregions.