Fort Prospect was the largest of three forts making up the Prospect Position. The other Forts were Fort Hamilton and Fort Langton. This is a polygonal fortification very similar to some of the other forts built as a result of the Royal Commission on the Defence of the United Kingdom set up in 1859.
Fort Prospect was built between 1865 and 1870. It was built to mount a total of twelve 64-pdr RMLs gun, mounted in pairs spaced around the whole perimeter of the fort. The guns were on Moncrieff disappearing carriages. There was a single large caponier at the rear of the fort covering the main entrance. The main magazine is just inside the main gate and has three chambers and a lighting passage.
Fort Prospect was converted to be a reservoir, initially in 1912 and expanded shortly after 1945. Much of the original trace of the Fort can still be seen but is covered with a layer of concrete from when it was used as a water catchment.