The Third Deep was a level in Khazad-dûm that had treasuries and armories. It was below the East Gate of Moria. During Balin's short recolonization of Moria, he sent Óin to find an access to it.
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Fellowship of the Ring, "The Bridge of Khazad-dûm"