History's Greatest Mysteries — Episode 1: Area 51

You are watching the episode Area 51 Hidden in the Nevada desert, a top-secret military base remains one of the most heavily restricted sites in the United States; since the 1950s, speculation has swirled about its true purpose-ranging from hiding experimental aircraft and even alien technology; Area 51 keeps its mysteries so closely guarded that not even the president is fully briefed; what is the government really hiding there?