Area 51 wasn't the only installation that the government has tried to keep secret from enemy nations. During World War II, the Army cloaked the Lockheed aircraft plant in Burbank, California with an elaborate camouflage to protect it from potential Japanese air attacks.
The Lockheed plant, as seen from above, prior to its camouflaging.
The same area, now hidden beneath a vast network of netting.
A street level view.
Close-up views above the complex.
A series of images from inside Lockheed, beneath the cloak of secrecy.