Blue Mountains, rugged plateau region on the eastern side of the Great Dividing Range, in the state of New South Wales, Australia, about 60 km west of Sydney. The name refers to the striking bluish colour of the mountains when viewed from a distance. The plateau reaches its maximum height of about 1,100 m in the west and then slopes gently towards the east. It consists of hard sandstone from the Triassic period, from about 200 million years ago, rivers have cut through the sandstone to the underlying rock, creating spectacular cliffs, canyons, and waterfalls. The Blue Mountains are a popular tourist spot for Sydney residents, favoured for the cooler summer temperatures and picturesque scenery. why so Blue?? The Mountains are covered with eucalyptus trees which constantly release very fine droplets of oil into the atmosphere. Only this week The Blue Mountains, have been placed on the National Heritage List.