Sentinel manufacturing facility
From Halopedia, the Halo wiki
A Sentinel Constructor Factory is a massive floating platform that produces Sentinel, Sentinel Major and Enforcer automatons.
Introduction
These facilities, float high above the ground, to keep them somewhat safe from the majority of Flood if there is ever another major outbreak amid the Installation. On the planet Onyx, there was a Sentinel Production Factory which constructed Onyx Sentinels every six seconds. It was later destroyed, by the Spartan-IIs and IIIs.[1]
Appearance
During Halo 2, they first appear in the level, Sacred Icon when the Arbiter reaches the inner abode of the Sentinel Wall.
There is an opening cleft, in the structure that is similar, to the opening where he first entered from the Phantom.
In the distance, above the Library, there are two large floating objects. Once the Arbiter exits the wall, one of these objects is hit, with a few plasma mortars, possibly fired from the Flood, to slow down the Forerunner defenses, from presumably a captured Wraith Tank and crashes down to the ground.
In the next level, you spy the same crashed structure, being pounded by Wraiths and Scorpions and fight through it as Sentinels and Flood fight each other.
While the appearance, inside the structure is badly damaged, some believe it to be a futuristic assembly line, allowing the Monitor, to have endless waves of Sentinels to control future Flood outbreaks.
