The way in is a 100-foot steel spiral staircase built in 1922 out of scrap from a First World War battleship: 144 steps, seven and a half turns, part of a 235-step descent to a floor 165 feet down. The chamber it lands in is the largest single cave room in California, tall enough to stand the Statue of Liberty inside without her pedestal. The name is the sound air once made moving through the passages, which the gold miners who found it in the 1840s heard before they saw anything.