Ered Lithui

Along the northern side of Mordor ran the Ered Lithui, the Ash Mountains, a long, grey and barren range that took its name from the ash that fell on it from Orodruin and from its own dull colour. At its western end it met the Ephel Dúath at the pass of Cirith Gorgor, where Sauron built the Black Gate and where the valley of Udûn lay in the angle between the two ranges. From there the Ash Mountains ran east for a great distance, with the plain of Dagorlad and the empty lands towards Rhûn on their northern side and the plateau of Gorgoroth beneath their southern cliffs. About midway along, a long spur ran south from the range onto the plain, and on it stood Barad-dûr. The mountains were pathless and no road crossed them; the Easterlings who came to Sauron's wars went round their eastern end or through the Black Gate.

The Ash Mountains fenced Sauron's realm from the Second Age. The Last Alliance came against Mordor along their northern face, fighting on Dagorlad before entering by the pass at their western end, and Gondor's Towers of the Teeth stood on the shoulders of that pass through the early Third Age. In March 3019 Frodo and Sam saw the range from the Morgai as the northern limit of the land they had to cross, and after the fall of Sauron the earth shook along its length as Barad-dûr collapsed from its spur.

The Ered Lithui ran east and west along the northern edge of Mordor from the Morannon, facing Dagorlad and the southern lands of Rhûn. Barad-dûr's spur lay roughly thirty miles east of Mount Doom.