From Halopedia, the Halo wiki
A habitat ring is a spinning, ring-shaped structure present on space stations. Various Lethbridge Industrial research and development space stations feature habitat rings. One such station, Auriga Station, was taken over by the Created, a rogue faction of AIs led by Cortana, some time after October 2558. In response to the takeover, the UNSC created a War Games simulation, codenamed "Torque," replicating a critical area on the habitat ring in order to train Spartan-IVs for an imminent assault on the location.