Pedro Rosa
Member
"One does not simply walk into Mordor. Its black gates are guarded by more than just Orcs. There is evil there that does not sleep. The great Eye is ever watchful. It is a barren wasteland, riddled with fire, ash, and dust. The very air you breathe is a poisonous fume."
—The Fellowship of the Ring, The Council of Elrond
Mordor's Borders
Mordor was a black volcanic plain in the southeast of Middle-earth to the East of Gondor, Ithilien and the great river Anduin. Mordor was chosen to be Sauron's fortress because of the mountain ranges surrounding it on three sides, creating a natural fortress against his enemies.
Mordor was protected from three sides by large mountain ranges, arranged roughly in a rectangular manner: Ash Mountains in the north, Ephel Dúath in the west and south. In the northwest corner of Mordor the deep valley of Udûn was the only entrance for large armies, and that is where Sauron built the Black Gate of Mordor.
in http://lotr.wikia.com/wiki/Mordor, 2015.09.22, 17h00