Udun

Udûn was a wide, depressed valley in northwestern Mordor. It lay between Cirith Gorgor and the Isenmouthe, and was traversed by large armies of Sauron in times of war.
Within its circumference were many Orc-holds, including Durthang, the forges, and the forts at Carach Angren.
== History ==
Udûn originated with the creation of the lands of Mordor. During both the War of the Last Alliance and the War of the Ring, the vast armies of Mordor passed through here and out the Black Gate to confront their enemies.