Installation 03 is one of the Seven Halo Rings. Very little is known about this installation, and it has to be yet directly observed for a more detailed description. It appears to have a red and cracked surface, indicating vast deserts and what appears to be volcanic activity. Although volcanic activity on Earth is caused by moving tectonic plates and the static, the artificial structure of the Halo rings would not allow such movement.
In 2552, during the Battle of Installation 05, a signal was sent to this Halo from Installation 05, putting it on standby mode. A readout from Installation 05's Control Room showed that Installation 03 was fully prepared to fire on demand.
A more comprehensive readout was later observed on the Ark, showing the inner part of the ring to be covered in what appears to be volcanic material, during the Battle of Installation 00 by the Arbiter, the Master Chief, and the High Prophet of Truth. It once again displayed that Installation 03 was on standby mode, ready to fire. However, the Master Chief deactivated the installation before it could be fired.
- This ring is often mistaken for Installation 05 because of the order the rings appear in The Covenant. Although it is not so, because Installation 05 is the 5th ring from the platform on which Truth and the Brutes reside rather than the direction in which the player enters the area, whereas the 5th ring in from the entrance has an apparently volcanic surface. The game files also confirm this.
- The numbering of the rings concerning the IWHBYD ring sequence is the opposite to the rings' actual installation numbers and should not be confused.