Billions of years ago, Primus created the hive-like Sanctuary hidden deep below the deadly Protos to hide the Covenant. He filled it with miraculous machines, which the Covenant strives (has striven?) to improve over the ages.
Parts of Sanctuary
A completely mirrored meditative chamber, used for self-examination. You must pass through the Reflectorium after decontamination when entering Sanctuary.
A location for theological discussion, research and debate. Libras and Scorpius engage in an endless high-spirited debate about the Theomachy in the Theosorium, fundamentally disagreeing about the nature and appearance of evil.
Sanctuary's nerve center. Cloaked spy satelites from across the galaxy beam information to the liquid computers here for collation and analysis. A vast trove of information of all sorts is stored here.
Meeting place of the zemstvo, the Covenant's voting council. Though the council lacks internal hierarchy, the others came to look to Leonicus's wisdom for leadership.
Sanctuary also houses the Covenant's armories; crystaline warcraft armed with indescribable weapons.
The Covenant's ships travel by folding space, not Transwarp. As a result, they are not capable of time travel, and had to be left behind when the Covenant braced Shokaract in the past. They traveled by personal Transwarp portal instead.