It was first settled over 100 years ago and has been used as a bacteriological station, quarantine station, a hospital to treat soldiers from WWI with venereal disease, mental hospital, a rehab for alcoholics, a women's jail, and now a sports and recreation centre.
Some of the activities available at Milson Island include a high ropes course, rock climbing, canoeing, kayaking, archery, bushwalking and abseiling.
The accommodation is 3-4 stars with seven lodges (Possum, Koala, Waratah, Kookaburra, Lorikeet, Platypus and Cockatoo) and five holiday units.
It is a popular place for camps for many schools across Sydney, and families go there for a nice, relaxed and fun retreat.
When the mental asylum was operating, an alarm system was set up, so that people on the island could keep themselves safe from mad escapees.