Is it the portal to the Ark?
No too sure.
Was it never revealed? Someone tell me.
If it WAS the ark, then why wasn’t Miranda keyes sure it was the ark.
“The covenant are looking for something. We have to assume its the ark”
M. Keyes.
On one hand, it’s probably glaringly obvious that down there was just the under ground control for The Ark to activate, so no one elaborated. People just looked at the fine text with there being none.
On the other hand, it really is a mystery and completely separate from The Ark and is something 343i can bring up anytime to throw a wrench into anything we know. 
Alright, thanks.
their keys
A teleporter?
Weren’t they trying to secure Vergil because he had merged with the Supercomputer and had all of the Covenant’s valuable data?
> Weren’t they trying to secure Vergil because he had merged with the Supercomputer and had all of the Covenant’s valuable data?
^this^
> Weren’t they trying to secure Vergil because he had merged with the Supercomputer and had all of the Covenant’s valuable data?
That’s part of it, but I think they were looking for the Ark as well. Without the ship controlled by the Prophet of Truth, though, it was guesswork.
Saber Khai