A photo of what used to be the 851st Strategic Missile Squadron, Titan 1 Intercontinental Ballistic Missile Complex 4C tunnels at Chico, Calif., May 23, 2013. Construction on the complexes began Jan. 22, 1960. More than 600,000 cubic yards of earth was excavated. In order to complete each facility, 32,000 cubic yards of concrete, 300 tons of piping, 90 miles of cables and 1,800 separate supply items were needed per complex. (U.S. Air Force photo by Senior Airman Allen Pollard/Released)

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Photo by: Senior Airman Allen PollardReleased |  VIRIN: 130523-F-EC341-003.JPG