OKB Zero

OKB Zero was a secret Soviet weapons design bureau operated in 1984 by XOF. It featured heavy security and at some point was used to house Sahelanthropus.

OKB Zero was originally a citadel build during the time of Alexander the Great, but it was left in ruins following one of Genghis Khan's compaigns. It's occupants changed numerous times and it was expanded on more than one occasion. Ultimately, it fell into the hands of the Soviet Philosophers. The Soviet Army was using it as the headquarters of its Afghan invasion force. Later, Skull Face used his connections with the Philosophers to develop Sahelanthropus there.

Soviet forces in the area were cooperative with XOF and even set up checkpoints on the way to the OKB Zero. Ultimately, though, they were betrayed by Skull Face and killed by the Russian strain of the vocal cord parasites.

At some point during his research for XOF, Huey was stationed in OKB Zero and had enough time there to learn the layout of the base.

Name
"OKB" is a designation the Soviet Union used for weapon design bureaus. However, the numbers that follow "OKB" are always above 1. It is unclear if the number "zero" was introduced by The Soviet and Chinese Philosophers to indicate that the facility was secret or if it was simply made up by Skull Face.

Behind the scenes
OKB Zero's helipad is inaccessible outside of the mission "Skull Face", the door to the helipad is closed.

Diamond Dogs' logo can be seen on some of the structures near the helipad in OKB Zero. It's unclear whether that's a mistake by the developers or a possible story hint.