masonry of the dam is a unique example of this type of gravity dam construction and demonstrates the principal characteristics of this technology. The lower valve house completed in 1907and extended in 1913 is a unique early example of its type and demonstrates the principal characteristics of the design of such structures. The water supply system completed in 1907 retains it gallery and rising main chamber in the dam wall, which demonstrate the principal characteristics of the design of such a delivery system. The grounds of the dam retain numerous tree plantings undertaken from the time of the completion of the dam and Manor in 1910. Collectively the diversity of these trees are an invaluable record of past horticultural practices. Terraces and platforms adjoining the dam abutments demarcate the location of plant used in the construction of the dam, in particular the location of the cableway head tower. The submerged basin of the reservoir is likely to retain remnant plant and equipment used in the construction of the dam, such as cuttings and terraces of the tramway. The site of the dam retains a number of known archeological sites which are associated with dam construction and later upgrading of the spillway. These sites include a large curved masonry dam on a tributary of Cataract Creek of the Appin/Bulli Road, a potential stone quarry, the formation of a roadway adjacent to the road of access, powder magazines on Keele Island and on the adjoining west abutment of the dam wall, and fireplaces, horse yard drains and powder magazines on the abutment adjoining the spillway. The place possesses uncommon, rare or endangered aspects of the cultural or natural history of New South Wales. Cataract Dam was the first major dam situated within a large water supply catchment area constructed in NSW. Cataract Dam is the oldest large cyclopean masonry dam constructed in Australia, and is believed to have been the largest works of its kind at the time of completion in the Southern Hemisphere. The straight cyclopean masonry wall is unique within the context of other large cyclopean masonry dams constructed in NSW. The lower valve house (completed in stages up to 1915) is the earliest and largest structure of its type constructed in NSW. The screen tower (completed in 1907) is the earliest structure of its type constructed in NSW, and includes unique water intake system. The crest house and valve