(Area 51 photographed in 1968)
A fascinating account of what happened when, in 1974, the Skylab crew inadvertently photographed the secret air force base at Groom Lake, Nevada:
“On April 19, 1974 someone in the CIA sent the Director of Central Intelligence, William Colby, a memorandum regarding a little problem.
“The issue arises from the fact that the recent Skylab mission inadvertently photographed” the airfield at Groom Lake. “There were specific instructions not to do this,” the memo stated, and Groom “was the only location which had such an instruction.” In other words, the CIA considered no other spot on Earth to be as sensitive as Groom Lake, and the astronauts had just taken a picture of it.”
Full story at: The Space Review