- "The CTU training grounds of the first and most iconic CTU. This is where SAS agents learn their craft and as such it a patchwork of plywood targets, sandbags, barbed wire and other obstacles. One of the most archetypal examples of siege gameplay."
— Ubisoft Description
Hereford Base is a map featured in Tom Clancy's Rainbow Six Siege. Formerly a non-flying station of the Royal Air Force from World War II to the end of the 20th century, It was redeveloped for use as a training ground for the Special Air Service.
The map was reworked in September 2018 with the release of the Operation Grim Sky expansion. This replaced the makeshift training facility with a more traditional brick structure. The original map is still playable in Situations.
The purpose of the map rework was to address issues with the map's flow, balancing, and visual thematic. Each floor of the facility now has a larger surface area, with more destructible floors and walls. News starcases and hatches were also added to increase movement between each floor. While the map has a dramatic change in the structure of each room, the general layout is very similar to the original map. The color palette for each floor was also changed in order for rooms to stand out more and provide players an easier way to coordinate strategies with one another.
- The original version of the map was a reimagined version of Kill House.