series of caves constituting one of Australia's best known tourist attractions, in east central New South Wales, 70 mi (113 km) west of Sydney. They comprise a series of tunnels and caverns formed by two converging streams in a thick bed of limestone at an elevation of 2,600 ft (800 m) on the western margin of the Blue Mountains. The caves are on different levels and contain unique limestone formations, particularly stalactites. They were once used by Aborigines, and James McKeown, a bushranger (outlaw), is said to have been the first European to visit them in the 1830s. They have been a government reserve since 1866. Twelve of the caves are open to the public, attracting more than 150,000 visitors annually.