Carn Dûm was a peak at the western end of the Mountains of Angmar. At about TA 1300, the Witch King of Angmar (Lord of the Nazgûl) began building a fortress and city there.

Carn Dûm served as the fortress and capital for the Witch King until he defeated the forces of Arnor and moved his capital to Fornost in TA 1974. In TA 1975, a combined force of elves from Lindon and Rivendell and men from Gondor defeated the forces of the Witch King on the plains west of Fornost and totally destroyed his forces. At that time Carn Dûm was abandoned.