Area 51 the base extends further east. After leaving the restricted area, Groom Lake Road descends eastward to the floor of the Tikaboo Valley, passing the dirt-road entrances to several small ranches, before converging with State Route 375, the "Extraterrestrial Highway", south of Rachel. Area 51 shares a border with the Yucca Flat region of the Nevada Test Site, the location of 739 of the 928 nuclear tests conducted by the United States Department of Energy at NTS. The Yucca Mountain nuclear waste repository is southwest of Groom Lake. Groom Lake is a salt flat in Nevada used for runways of the
Area 51 the judge, the land that overlooked the base was taken to address security and safety concerns connected with their training and testing. The amount of information the United States government has been willing to provide regarding Area 51 has generally been minimal. The area surrounding the lake is permanently off-limits to both civilian and normal military air traffic. Security clearances are checked regularly; cameras and weaponry are not allowed. Even military pilots training in the NAFR risk disciplinary action if they stray into the exclusionary "box" surrounding Groom's airspace. Surveillance is supplemented using buried motion sensors. Area 51 is a