In J.R.R. Tolkien's legendarium, the Mines of Moria (Khazad-dum) were built by the Dwarves, specifically by Durin the Deathless in the First Age. The mines were a vast underground complex and the greatest of all Dwarf works. Orcs later occupied it after the Dwarves fled, and Elves and Hobbits never built mines like Moria.