In Tolkien's mythology, Morgoth's First Age fortress was called Angband.
Angband was a vast underground stronghold in the north of Middle-earth. Morgoth, the chief enemy of the Elves and the first Dark Lord, used it as the center of his power during the wars of Beleriand. The fortress was protected by the Iron Mountains and commanded by dragons, Orcs, and other servants.
The name Angband means “Iron Prison” or “Iron Hell” in Tolkien's Elvish terminology. It was associated with the pits where Morgoth bred and armed his forces, and with the great gate defended by the dragon Glaurung and later by Ancalagon.
Angband is distinct from Utumno, Morgoth's earlier fortress in the far north. Barad-dûr was Sauron's later fortress in Mordor, while Isengard belonged to Saruman during the events of The Lord of the Rings.