Moria

Moria, also known as Khazad-dûm, is an ancient underground city in the Misty Mountains of Middle-earth. It was the greatest stronghold of Durin's Folk, the Longbeards, and long served as a major mining and trade center for the dwarves. The city lay beneath the western slopes of the mountains and was entered by the West-gate, the Doors of Durin. Its vast halls, carved passages, and subterranean river systems supported a sizable population and a sophisticated dwarven industry, notably the mining and processing of mithril.

Khazad-dûm was founded by Durin I in the early Second Age and soon grew to be the dwarven capital and a repository of craft and knowledge. The dwarves expanded the mines beneath the city, producing great wealth from mithril, and constructing immense halls such as the Hall of Durin and the Chamber of Mazarbul. Over time, heavy mining and the perils of the underground weakened the city’s foundations. In the depths, a Balrog—known to dwarves as Durin's Bane—was awakened, driving the dwarves to abandon Moria.

In the Third Age and beyond, Moria remained largely deserted, though it remained a place of memory for dwarves and a hazardous waypoint in epic tales. In The Lord of the Rings, the Fellowship of the Ring traverses Moria, discovering Balin's Tomb in the Chamber of Mazarbul and crossing the Bridge of Khazad-dûm, where Gandalf battles the Balrog and falls into the abyss, later to be restored as Gandalf the White. The Doors of Durin also figure prominently as the gate to the underground realm.