After years of denial, the CIA finally 'fessed up: Area 51 really does exist! The mysterious airbase in Nevada was revealed in recently declassified documents:
According to these reports, which include a map of the base's location in Nevada, Area 51 was merely a testing site for the government's U-2 and OXCART aerial surveillance programs. The U-2 program conducted surveillance around the world, including over the Soviet Union during the Cold War. [...]
The map and other documents were released in response to a Freedom of Information Act request submitted by Jeffrey T. Richelson, a senior fellow at the National Security Archives, in 2005.
Richelson submitted the request as part of his continuing study of aerial surveillance programs and told CNN that he was not given an explanation of why the new documents were less redacted than previous versions declassified by the agency.
They still, however, won't let us see the aliens on the base.