Foundry (location)
From Halopedia, the Halo wiki
The Core of the Ark (Installation 00) is believed to be planetoid which may have been taken from the Milky Way as it was sustainable for life. The Ark itself was built arround 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 the Earths size but would have been a lot bigger as the Foundry arround the planet could have held a planet two or theee times the size of core. It the heart of Installation 00 and is likely to be the power source.
The Planet itself is almost hidded by clouds and is covered with storms. It is roughly 4251km in diamiter. It may have been taken from the Milky Way by using a Micro Dyson Sphere to trasport it to the Ark. It would have been an inhabitable planet before it was stripped down for raw materials. The Core may have an effect on the enviroment around it and help give an atmosphere to the Shield Worlds that are constructed arround it.
Protection
Both the Core and the Foundary 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 crashlands on the Ark.
