Were you also looking for The Silent Cartographer, which is a level in Halo: SPV3?
On Installation 04, the Cartographer was located in the middle of a large island. The security system was located in a tunnel, atop a large Forerunner structure in about the center of the island. After disabling the security system, the main passageway to the map room was opened. For additional security measures, the Cartographer's chamber and activation panel were located on the other side of the island, and buried at least half a dozen floors below ground. The path down to the Cartographer is a labyrinth of twists and turns, making it easy to get lost. This could also be part of the security system, to make the map room harder to find. It seems that on the map, the Control Room is illustrated as a shrine.
In 2552, John-117 and two squads of ODSTs were ordered by Captain Keyes to attack the Cartographer so that they could locate Halo's control room. The soldiers landed on a Covenant-controlled beach which was quickly captured. While taking shelter under an enormous structure, John and his ODSTs received a Warthog from Echo 419. John and two ODSTs used the Warthog to get to the entrance of the facility. John captured the entrance but was locked out of the lower areas. They then went back to the Warthog and found the island's security center, guarded by many Covenant forces and an ambush by two Hunters. After unlocking the map room, the Spartan headed back to the Cartographer and fought his way down to the map. Once on the surface again, John went to the newly located Control Room with the help of Echo 419.
The Installation 04 Cartographer was protected by an elaborate security system. This system can only be activated and deactivated by manual physical contact. In order to access the Silent Cartographer one must enter a first building to disable the security system, and then enter a separate structure which contains the map room. This gives the map room double protection making access difficult and defense much easier. The weaponry wielded by the crew of the Pillar of Autumn was not powerful enough to penetrate the doors inside the facility where the Silent Cartographer was located, indicating the doors were of extremely durable material. Other than near impenetrable doors, both physically and in protection against AI, the nature of the Silent Cartographer's security system is not touched upon.
- The interior details and layout of the Cartographer on Installation 04 is almost completely identical to that of the Ark's Cartographer complex, though it is almost impossible to notice, due to the differences in textures, scenery, and atmosphere that were made to the structures to make them appear unique. In addition, practically the entire length from the first staircase to the main chamber of the Ark's Cartographer complex is a complete remake of Installation 04's Cartographer.
- The Silent Cartographer is oddly named because a cartographer is someone who makes maps, not a map itself. This may imply that the Silent Cartographer is more than just a building; possibly an old Forerunner computer. This could be supported by 343 Guilty Spark stating upon arrival at its controls that "it awaits your approval," possibly meaning it was aware of the nearby Reclaimers and was expecting activation.
- It is unknown if all Forerunner structures have a Cartographer, though it is likely all Installations possess one.
- The Cartographers always seem to appear over a chasm.