Ammunition Igloo - Credit: Wikimedia Commons
Ammunition Igloo (also known as Building 88) was a bunker used for arms storage at Camp George West, Golden, Colorado. It was built in 1940 of stone, supported by a soil-covered concrete arch. Rubble masonry, built of basalt, was used for the parapet-equipped facade., page E-41. Read more on Wikipedia
Source: en.wikipedia.org