Cockatoo Island Tunnel by Paul Carmona (Australia Photo Spot)

At 180m long, this dark tunnel weaves its way through the belly of Cockatoo Island. Built in 1915 to move workers and materials from one side of the island to the other, when World War II broke out the tunnels were used as air-raid shelters. One of them was even kitted out with an infirmary located in an annex to the main tunnel. Over the past 175 years the island has been a jail, a graving dock, a site for a girls’ reformatory, and a major shipbuilding site. Plus more recently an arts venue, a top viewing spot for the New Year’s Eve fireworks, a film set and now a unique campground. (Sydney Harbour, New South Wales, Australia)