Its modern purpose is still undecided, but the historic significance of Prospect Reservoir is not up for debate.
The 50,000 megalitre water supply was an engineering marvel at the time of its construction in the late 19th-century.
Today it exists mainly as a recreational area, and its importance to Sydney’s water supply is limited to a backup emergency source.
The state government has started a risk assessment to see whether the site could be suitable for fishing and other aquatic activities – a proposal pushed by the Greater Sydney Commission and long supported by Blacktown Council.
Edward Pincott is another fan of the idea.
Mr Pincott, 78, is a descendant of brothers Thomas and George Pincott, who helped make the ambitious project a reality more than 100 years ago.
He recently helped organise a reunion at the reservoir with about 60 members of the Pincott and Fisher families, who have a long association with the site.
“It was a great day. The sun was shining, everybody was happy,” Mr Pincott said.
Much of the family was excited to see the Pincott roller, which was used to compact the earth around the site.
The heavy piece of equipment was transported from Ballarat by a team of bullocks in the 1860s.
“You can imagine pulling that up and down a hill. It wouldn’t have been an easy job,” Mr Pincott said.
“People still ask us if we’ve got anything do with it. It’s part of our heritage.”
Mr Pincott said he would like to see the dam opened to fishing for western Sydney’s growing population – a decision ultimately up to WaterNSW.
The site exists in a curious limbo, where Sydney Water owns the land including the heritage buildings and picnic areas, but the state body owns the water.
Sydney Water lead heritage adviser Phil Bennett said the scheme that saw the creation of the dam, which used gravity to direct water from the upper reaches of the Nepean Rover on the Wollongong escarpment to Circular Quay, was a remarkable engineering feat.
“The Upper Nepean Scheme was an enormous scheme in the day...it was an amazingly big piece of infrastructure, so they created the water board to manage it. And that’s the beginning of Sydney Water. So to Sydney Water, Prospect has a pretty special place,” Mr Bennett said.
The site is also a significant part of Australia’s settlement history, featuring a homestead built and owned by explorer William Lawson, who is laid to rest in Prospect.
Mr Bennett said the foundations of two convict-era buildings remain on the site, which was also used by light horse cavalry for training during World War I.