One of the last Martello Towers to be build in the world after the design's defensive capabilities had been proven by the English at Cape Mortella Corsica in 1794. The fort was built to defend Sydney against possible attack by Russian warships. Built from 8000 tonnes of sandstone quarried near Kurraba Point at Neutral Bay, the fort was named after Sir William Denison, the then Governor of New South Wales.
Fort Dension was once little more than a rocky outcrop and was a prison island for Sydney's worst prisoners from 1841 to 1857 and was often known as Pinchgut. The local Aborigines referred to the island as Mattewai or Mattenways before white settlement. The fort is used today as a tide gauge station.
A number of tours of the island are available including: Fort Dension Heritage Tour Monday to Sunday - 11.30am to 3.15pm (set arrival and departure by ferry only) Saturday and Sunday - 2.30pm to 5.15pm Afternoon tours are available Monday to Friday at 2.30pm subject to demand Fort Brunch Saturday and Sunday 9.00am to 11.40am. You can eat at the cafe or take a picnic lunch.