It is one of Sydney Habour's hidden gems. A sprawling precinct, dotted with empty warehouses and old factories, overlooking the water on Sydney's north shore.

For more than 150 years it has been closed to the public.

But all that is about to change. The Sydney Harbour Federation Trust is opening up the 1.8 hectare site in the hope it will become Sydney's newest cultural and commercial hub.

Located less than a kilometre from North Sydney's CBD, the site was once a gasworks factory and later became a submarine base known as HMAS Platypus.