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 came to the Air Force's Project Blue Book, which investigated UFO sightings, through air-traffic controllers and letters to the government. The project checked U-2 and later OXCART flight records to eliminate the majority of UFO reports it received during the late 1950s and 1960s, although it could not reveal to the letter writers the truth behind what they saw. Similarly, veterans of experimental projects such as OXCART and NERVA at Area 51 agree that their work (including 2,850 OXCART test flights alone) inadvertently prompted many of the UFO sightings and other rumors: They believe that the rumors helped maintain secrecy