Regarded as Australia's most outstanding cave system, with pure underground rivers and amazing limestone crystal formations, Jenolan Caves, located 30 km south-east of Oberon, is one of the finest and oldest cave systems in the world. The Cathedral Chamber of the Lucas Cave is reputed to have the finest acoustics of any performance space in the world. Jenolan is known as an ‘impounded' Karst, as the limestone receives water from the surrounding insoluble rocks. Caves and karst features are produced because limestone is soluble in water containing dissolved carbon dioxide. Rain absorbs CO2 from the atmosphere thus providing the catalyst for the creation of this remarkable place.