Munitions bunker
One of the original 1950s munitions bunkers in the early stages of demolition is seen here Aug. 31, 2015, at Fairchild Air Force Base, Wash. The concrete bunkers were covered with many feet of soil, giving them a hill-like appearance, to ensure an accidental explosion would be buffered and not cause a chain reaction. (U.S. Air Force photo/Airman 1st Class Mackenzie Richardson)