Area 51 UFO site. Signs warning against trespass from Area 51 in Nevada, USA. It is alleged that research is conducted at Area 51 into crashed UFOs (Unidentified Flying Objects) & their alien crews. It is claimed that UFO technology is copied, & that aliens live there. Area 51 is a highly-secret military research base which does not appear on maps. It lies in Groom Dry Lake, about 190 kilo- metres northwest of Las Vegas. The surrounding Papoose Mountains hide it from view, and warning signs and security guards deter trespassers. Area 51 was opened in 1954 and its 8 kilometre-long runway is the longest in the world. It has been used to develop many American military aircraft.