Control room

Were you looking for the Ark's control room, the Citadel?

Each of the Halo Installations created by the Forerunners has a central Control Room. The Control Room contains the Installation's Core data center, and is where the Index is used to activate the Halo's weapon. It is typically located within a pyramidal temple-like structure.

Installation 04
Installation 04's Control Room was located in a snowy chasm. The main console and Core was located within a massive spherical chamber behind a set of doors and connecting corridors. The room features a massive hologram of Installation 04 and the Threshold system in its center. Suspended in the air is a large circular catwalk.

The Master Chief reached the main console and inserted Cortana, who sent him to the installation's Flood containment facility to attempt to stop Captain Keyes from unleashing the Flood. He returned to the Control Room at the start of Two Betrayals to insert the Index as prompted by 343 Guilty Spark, but was stopped by Cortana. 343 Guilty Spark then sent Sentinels to stop the Chief. After the Chief destroyed the Sentinels, he took Cortana and left.

Installation 05
Installation 05's Control Room is located on an offshore island in a large body of water. It bears significant structural differences from Installation 04's room.

Here, the Jiralhanae Chieftain Tartarus brought Miranda Keyes to the Control Room along with 343 Guilty Spark to attempt to activate Delta Halo. He succeeded in activating the installation, but was slain by Thel 'Vadamee and Sergeant Johnson. The Index was removed by Miranda before the weapon could fire. It consists of a three-leveled structure with a gravity lift in the middle. On all three levels, there are many crates containing Brute Plasma Rifles and Carbines.

Installation 04B
The Control Room for the replacement Installation 04 is a nearly identical copy of the original ring's Control Room.

The temple structure has the same basic triangular shape as Installation 04's Control Room, with a long support beam running from the ground to the top of the structure. There are minor aesthetic differences, including the walkways on each level being more narrow, as well as the tower at the top being replaced by a large flat landing.

As you progress into the control room, the corridors and doorways are reminiscent of Installation 04, while offering minimal changes. The actual control room and control panel is scarcely different from the original. The large dome-shaped room still shows a holographic image of the halo ring, although Threshold is missing from this image (as the ring has not been moved to that point).

The differences in design from the original Installation 04 may be due to the ring's incomplete state, as suggested by Cortana's observation, "Halo. It's so new...unfinished." This "newer" design could also be what Installation 04 originally looked like before the Flood outbreak and the activation of the Halos by the Forerunner.

Trivia

 * The control room was first seen in the pre-Xbox Halo demo in 1999. In the video, the control room was about one-third the size of the version later seen in Halo: Combat Evolved.
 * It is most likely that the appearance of the Control Rooms differ with each Installation, since the design of the one found on Installation 04 bears little resemblance to that of Installation 05. Given that not all of the Halo rings known to have existed were built concurrently, it is possible that Installation 05's design was of an earlier/later version than that of Installation 04.

List of appearances

 * Halo Combat Evolved
 * Halo 2
 * Halo 3
 * Halo Legends
 * Origins
 * Halo: Silentium