13 Abandoned Cold War Bunkers Hiding Incredible Secrets

9. Site R (Raven Rock Mountain Complex), USA: The "Underground Pentagon"

Tucked away in the mountains near the Pennsylvania-Maryland border lies Site R, another critical US continuity-of-government and military command bunker. Often dubbed the "Underground Pentagon," its exact capabilities and current functions remain highly classified, although it's known to be a major communications hub and relocation site. Its enduring secret lies in its continued operational status and the intense secrecy surrounding its modern role within the US national security apparatus – a Cold War fortress still very much alive and hidden.