Location from Half-Life 2 by Valve
Where it all started — the underground research complex in New Mexico where a routine experiment tore open the fabric of reality.
Black Mesa is the origin point. The resonance cascade — caused when Gordon Freeman pushed an anomalous material sample into the Anti-Mass Spectrometer — tore open a portal to the Xen borderworld, flooding the facility with alien wildlife and drawing the attention of the Combine. The facility's destruction by nuclear strike failed to close the portals permanently. The dimensional breach attracted the Combine, who invaded Earth and won the Seven Hour War. Every character in Half-Life 2 who survived Black Mesa carries the weight of having been present at the end of the old world. Black Mesa's legacy shapes everything: the teleportation research that the resistance uses, the relationships between surviving scientists, and the guilt of those who wonder if any of it could have been prevented.
A vast underground research facility in the New Mexico desert, built into a decommissioned ICBM silo complex. The surface shows little — a few concrete buildings, a rail line, desert. Below ground, miles of corridors connect research wings, test chambers, reactor facilities, and living quarters. By the events of Half-Life 2, Black Mesa is a radioactive ruin — destroyed by a nuclear warhead deployed to contain the resonance cascade. It exists now only in memory and in the scattered survivors who carry its knowledge.
Also known as: Black Mesa, BMRF, The Facility, The Mesa