Foundry (location)

The Core of the Ark (Installation 00) is believed to be planetoid which may have been taken from the Milky Way galaxy as it was sustainable for life. The Ark itself was built around it and it would have been used as raw material for constructing the Ark and other Shield World installations.

Structure
The planet itself is about 1/3 of Earth size but would have been substantially bigger as the Foundry (not to be confused with the multiplayer map) around the planet could have held a planet two or three times the size of the core. It the heart of Installation 00 and is likely to be the power source.

The Planet itself is almost hidden by clouds and is covered with storms. It is roughly 4255 km in diameter. It may have been taken from the Milky Way by using a Micro Dyson Sphere to transport it to the Ark. It might have been an inhabitable planet before it was stripped down for raw materials. The Core may have an effect on the environment around it and help give an atmosphere to the Shield Worlds that are constructed around it.

Protection
Both the Core and the Foundry are protected by an energy shield which is designed to stop the Flood from entering the Foundry. A small section of it is disabled in The Covenant to gain access to the Citadel but the Flood make a new foothold there when High Charity crash-lands on the Ark. If the Core survived Installation 04 there is a chance that Sentinels would repair the Ark.