Cerin Iaur (S."Old Mound";Hi."Cairn Sen"), was an ancient keep on the edge of the Coldfells in northeastern Rhudaur. Once the castle of one of the five Tiri, the Dunadan feudal lords of Rhudaur, it later became an outpost of the Hillman-King's power in the center of the country. It also guarded a useful caravan route between Morva Tarth and the Misty Passes.