The Umbrella Research Center (also known as the Umbrella Management Training Facility) is the central location during the events of Resident Evil Zero. Located in the Arklay Mountains roughly ten miles from Raccoon City, this facility was once dedicated both to training those who would become Umbrella's leading executives and to Progenitor virus research during the corporation's early years. The facility was first established in 1968 by Umbrella's co-founder James Marcus and was closed down twenty years later following Marcus' assassination.
From the late 1960's to late 80's, the Research Center was used by James Marcus primarily for his research into the properties of the Progenitor virus which had initially been discovered in Africa. It was in this place that Marcus first discovered the T-virus after infusing leeches with Progenitor, creating a very different life-form altogether that possessed significant military potential. As Marcus' experiments continued, the leeches he had cultivated grew in intelligence, developing a hive mentality.
In 1988, Oswell E. Spencer - president of Umbrella - deemed Marcus a liability and ordered Marcus' two most trusted researchers, William Birkin and Albert Wesker, to assassinate him. Following the assassination, Marcus' body was dumped in the sewage plant beneath the facility, Birkin was credited for Marcus' viral research and the facility itself was shut down and abandoned.
In the summer of 1998, Umbrella planned to reclaim the Research Center, but the advance teams they sent in to accomplish this task were attacked by infected leeches controlled by the resurrected James Marcus. This clone of Marcus had taken over the facility and made it his lair from which he intended to launch a campaign of revenge against Umbrella. However, his plans were ruined thanks to the interlopers Billy Coen and Rebecca Chambers, who worked together to fend off the numerous creatures infesting the facility and kill the mutated Marcus. The Research Center was then destroyed when Birkin remotely activated the facility's self-destruct system.
- Zombies - Human T-virus carriers. These unfortunate subjects consisted of Umbrella researchers and paramilitary troops assigned to re-opening the Research Center, only to have been infected by Marcus' leeches.
- Infected crows - Crows that contracted the T-virus after feeding on infected flesh.
- Web Spinners - Spiders that may or may not have been deliberately infected with the virus.
- Infected bats - Bats that nested in the belfry of the Research Center's church. They became infected after attempting to feed on the leeches.
- Centurion - A centipede mutated to an enormous size.
- Eliminators - Monkeys infected with the T-virus; the first mammalian B.O.W.'s Umbrella ever developed.
- Infected leeches - While Umbrella never saw much practical use for leeches in bio-warfare, the resurrected Marcus was capable of controlling these creatures mentally. Massive clutches of leech eggs could be found throughout the Research Center and the leeches themselves were capable of joining together to form humanoid figures that would attack intruders.
- MA-121 Hunter "α" - Located in the B.O.W. testing area in the facility's lower levels.
- Plague Crawlers - Giant arthropods that primarily dwell in the facility's basement.