Installation 04's Control Room was the site that controlled all of the Installation's operations.
- “Unfortunately, my usefulness to this particular endeavor has come to an end. Protocol does not allow units with my classification to...perform a task as important as the reunification of the Index with the Core. That final step is reserved for you, Reclaimer.”— 343 Guilty Spark
The Control Room is located in a subterranean level below the surface of Installation 04. The facility was built directly into a giant artificial cavern and protected by several sets of massive, presumed blast-proof, doors.
Inside there is a large circular bridge that lacks supports. The bridge ends in a circular walkway. Both the bridge and walkway are made out of a reflective metal. In the center of the walkway there is a hologram of Threshold, Basis, and the ring between the two. On the outside of the walkway there is a model of the Halo ring itself. The model displayed a detailed map of the terrain and slowly rotated.
There is a single computer terminal in the room where the Index can be inserted to activate the rings. The terminal also reported the weather, rate of spin, information on the machines keeping the ring running, and information on the outbreak of the Flood.
For thousands of years, the ring and it's control room were completely derelict. In 2552, after the UNSC ship Pillar of Autumn crashed landed on the ring, Covenant scouts came across the control room, presumably through use of the Silent Cartographer.
When the Master Chief John-117 came across the control room, he integrated Cortana into the interface. Absorbing the wealth of knowledge, she informed him of a terrible secret and sent John after Captain Keyes and his squad who were going after a Covenant weapons cache.
Later, Halo's Monitor, 343 Guilty Spark, brought John back to the control room in order to activate the ring. When he learned what the ring's true function was, John yanked Cortana out of the panel and raced to stop the activation process.
- It has been noted that when viewed from the top, the main console room resembles the Marathon logo.