The Blue Mountains is a mountainous region in New South Wales, Australia. It borders on Sydney’s metropolitan area, its foothills starting approximately 50 kilometres west of the NSW capital.
Consisting mainly of a sandstone plateau, the area is dissected by gorges up to 760 metres deep. The highest point of the range is 1,190 metres above sea level. A large part of the Blue Mountains is incorporated into the Greater Blue Mountains Area World Heritage Site, consisting of seven national park areas and a conservation reserve.
The Blue Mountains area includes the local government areas of the City of Blue Mountains, the City of Hawkesbury, the City of Lithgow and Oberon.
The Jenolan Caves are remarkable caves in the Blue Mountains, New South Wales, Australia; 175 kilometres west of Sydney, easily accessed by driving. They are the most celebrated of several similar groups in the limestone of the country being the oldest discovered open caves in the world. They include numerous Silurian marine fossils of great interest and the calcite formations, sometimes pure white, are of extraordinary beauty. The cave network is enormous – over 40 km of multi-level passages – still undergoing active exploration. Several kilometres of the caves have been rendered easily accessible to paying visitors and are well lit.