" Clandestine Service, tells us a story about the building at the center of the Pentagon courtyard, which is now a food court but used to be a hot dog stand. Chesnutt explains that during the height of the Cold War, when satellite technology first came into being, Soviet analysts monitoring the Pentagon became convinced that the building was the entrance to an underground facility, like a nuclear missile silo. The analysts could find no other explanation as to why thousands of people entered and exited this tiny building, all day, every day. Apparently the Soviets never figured it out, and the hot dog stand remained a target throughout the Cold War—along with the rest of the Pentagon. It’s a great anecdote and makes one wonder what really is underneath the Pentagon, which is rumored to have multiple stories belowground. "

― Annie Jacobsen , The Pentagon's Brain: An Uncensored History of DARPA, America's Top-Secret Military Research Agency