I live near and work even closer to this very interesting facility. It used to be the Federal Reserve System's Communications and Research Center (a pretty important part of the Federal Reserve System), and it also served as an emergency "continuity of government facility" at one time. Check these links for your browsing pleasure (links have pictures, Google search "Culpeper Federal Reserve" gives lots of info)
heh, I can't post fast enough... someone beat me to submitting this. Looks like I duped Link3.
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