A US military installation located in Nevada, USA. It is officially known as Groom Lake Air Force Base. The base is completely off-limits, giving rise to theories that it is a UFO crash site or an alien research lab. The base is crisscrossed by numerous runways, leading some to speculate that it is used to test prototype military aircraft.
In 2011, Raiden was imprisoned by the Patriots at Area 51 after rescuing Sunny. There, he was subjected to experimental surgery that implanted an enhanced exoskeleton and reshaped his entire body. Raiden later escaped from Area 51 with the help of the Paradise Lost Army.