The Secrets of Area 51

Area 51 is guarded more heavily than some of the United States' most sacred buildings, including CIA headquarters in the Pentagon. Many of the buildings did not have windows, so workers could not see what was really being worked on. They even had many teams working on different parts of the same project without collaboration. Even after the satellites made these spy planes obsolete, the government continued to deny Area 51 even existed until a 2013 report.