Cockatoo Island Wareamah is a UNESCO World Heritage Site at the confluence of the Parramatta River and Lane Cove River in Sydney Harbour, New South Wales, Australia. Cockatoo Island is the largest of several harbour islands that were once heavily timbered sandstone knolls. Originally the Island rose to 18 m above sea level and was 12.9 hectares but it has been extended to 17.9 ha and is now cleared of most vegetation.