Underground Worlds S02E02 - Grand Canyon's Lost Treasure

Inside the Grand Canyon Caverns, North America's largest dry cave system, the eastern European cave city of Vardzia in Georgia, plus, the hidden UK Cold War bunkers which played a pivotal role in monitoring for incoming nuclear bombers. Peek inside a bunker which has never been seen on TV before, and another that has been faithfully restored to how it would have been when the Cold War tensions were at their highest.