Dwarves built the underground city of Khazad-dûm in J.R.R. Tolkien’s Middle-earth.
Khazad-dûm, also called Moria by the Elves, was the greatest mansion of the Dwarves in Middle-earth. It lay beneath the Misty Mountains and became famous for its vast halls, mines, bridges, and wealth of mithril, a precious metal prized by the Dwarves.
The city was founded by Durin the Deathless, one of the Seven Fathers of the Dwarves. Its prosperity ended after the miners awakened a Balrog, later known as Durin’s Bane. The Dwarves abandoned the city, and by the time of The Lord of the Rings it is a dangerous ruin occupied by Orcs and the Balrog.
The two names can cause confusion: Khazad-dûm is the Dwarvish name, while Moria is the Elvish name. The city is therefore not an Elven creation, even though Elves used the name Moria and had important historical connections with the region.