Halo 4 : Requiem

Ah, Requiem's Cartographer. While it only saw one battle during the Requiem Campaign, it is still important. After the Chief left, the structure apparently locked it's doors to the Covenant, keeping them out until the entrance was recaptured by the UNSC. While the UNSC never got the Cartographer itself to activate due to what appeared to be Covenant plasma damage to the central control console, it still was a pseudo-important location in the Requiem Campaign.