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
Oklahoma State Highway 51 area. In Sand Springs, SH-51 crosses the Arkansas River with SH-97 before merging onto the Sand Springs Expressway (U.S. Highway 412/U.S. Highway 64). When this freeway ends at I-244 near downtown Tulsa, Highway 51 merges onto I-244 southbound only to exit one mile (1.6 km) later, where it overlaps US-64/US-75. This freeway is actually Interstate 444, but the interstate designation is not shown on signs. After one more mile, SH-51 leaves the interstate with US-64 and becomes the Broken Arrow Expressway, a freeway running northwest-southeast through Tulsa which is known as "The BA" by locals and local media. US-64 leaves