Black Mesa Research Facility is a secret facility located in the New Mexico desert. Its main activity is scientific, but some of its units carry prototypes of new weapons. It was founded in the 1950s around an intercontinental ballistic missile silo as a supply base and weapons depot, but later changed its purpose to another.
The complex is divided into many Sectors, each of which performs its own function. All of them are controlled by various administrators headed by Dr. Breen. He is also the head of the Complex.
Speaking of Sector Delta, most of the Black Mesa personnel are unaware of its existence. The exception is Dr. Breen and some Sector █ scientists who have a high level of clearance. We sometimes exchange data with them or enter into mutual assistance agreements.
Despite her secret status, Black Mesa is regularly attacked by terrorists calling themselves the "Xen's Brotherhood". Their leader, Dr. ████████, who formerly worked in Sector █, is responsible for many incidents, including the very first one, X-0. In order to resist attacks, many sectors are now protected by multiple checkpoints with huge metal doors and turrets. They are also intended in case of an emergency related to experiments.