The Hall was located deep in Angband and was approachable from an unknown number of portals cut into the rock. Presumably, it was a very large place in portion as Morgoth was very large. It was a place of utmost fear and horror with brightly lit fires, horrible-looking pillars that towered like trees boughs like serpents, and was filled with weapons and instruments of death and torture. Across the hall stood a monstrous column and beneath it was the throne of Morgoth.
The Nethermost Hall was possibly delved and raised when Angband was built or when Morgoth returned there from Aman after stealing the Silmarils. As he rarely left Angband, Morgoth probably spent most of his time here plotting his evils, torturing, and interrogating helpless prisoners. The Nethermost Hall was best known for being the place where Beren and Lúthien confronted Morgoth when he lost one of the Silmarils to Beren.