Beneath the island’s rainforest, explorers search for new discoveries deep within some of the Earth’s largest, longest, and wildest caves ... walls with plenty of room to spare.

To mark the anniversary of its completion we've looked back at the planning and building of the famous structure, including a last minute change of plan and why there is a hidden cave inside.

In the middle was a man-made, semicircular stone cave lined with benches and kerosene lamps. But in the 1960s the cave became a magnet for vandals, and by the late 1970s the Parks Department had ...