Underneath the Island, in the areas not hewn away to make room for heavy industry, Cockatoo island is criss-crossed with a myriad of tunnels, facilitating the movement of people, materials and equipment across the island. These also served a dual purpose as an air-raid shelter for use in the Second World War: one was even kitted out with an infirmary located in an annex to the main tunnel. Another tunnel has an elevator running right down into it from the buildings atop the island, down through the rock.