Black Mesa Research Facility

The Black Mesa Research Facility is the primary setting for Half-Life and its three expansions, Opposing Force, Blue Shift and Decay. The base is a decommissioned ICBM launch silo in the New Mexico desert that has been turned into a scientific research complex. The facility is depicted as a vast complex of underground research laboratories as well as surface constructions such as offices, chemical waste disposal plants, and personnel dormitories, all powered by a hydroelectric dam and connected by a tram system.

Over the course of the series, Black Mesa is revealed to be conducting top-secret research into various fields, such as teleportation and experimental weapons research. Prior to the beginning of Half-Life, scientists experimenting on teleportation discover Xen, a border dimension somehow intricately involved in the teleportation process. Creatures and crystals from Xen are consequently brought back to the facility for testing. At the beginning of Half-Life, one such crystal, revealed in Episode Two to have been provided by the G-Man, is put through an anti-mass spectrometer and causes a resonance cascade, tearing the spacetime continuum. As a result, Xen creatures are teleported into the facility and prey on its human inhabitants.

The resulting crisis is seen from several points of view in Half-Life and its expansions. In Half-Life, protagonist Gordon Freeman is introduced to the facility in a notable sequence involving very little interactivity. This serves to foreshadow many of the challenges the player will face, as well as the labyrinth-like structure of the game. Eventually, the player fights through the facility and teleports to Xen to try to seal the tear from the other end, where a Xen creature is keeping it open. Blue Shift shows the events from the viewpoint of a security guard, Barney Calhoun, who joins a group of scientists who use the teleportation technology to evacuate survivors from the base. In Decay, another group of scientists attempt to close the tear through their own equipment, before calling in the US military to assist with the situation. The military situation is shown through the eyes of Adrian Shephard in Opposing Force, where US Marines are ordered to kill the entire population of Black Mesa as well as the alien attackers, but are overwhelmed and forced to withdraw, allowing for black operations units to detonate a nuclear warhead in the facility, ultimately destroying it. However, the fracture in the spacetime continuum remains, allowing the Combine to invade and occupy Earth.