Mordor
Mordor, meaning the Black Land or the Land of Shadow in the Elvish tongue, is the realm of Sauron the Dark Lord in the southeast of Middle-earth. A vast, ash-strewn, and desolate land ringed by mountains, it is the seat of Sauron's power and the location of Mount Doom, the volcano in whose fires the One Ring was forged and where alone it can be unmade. Mordor is the destination of Frodo and Sam's perilous quest in The Lord of the Rings.
Mordor is guarded on its western and northern sides by great mountain ranges that make it a natural fortress. Within lie the plain of Gorgoroth, the inner sea of ash and the dark tower of Barad-dûr, from which Sauron rules.
Geography
Mordor is enclosed by three mountain ranges: the Ered Lithui, the Ash Mountains, along the north, and the Ephel Dúath, the Mountains of Shadow, along the west and south, with a spur where the two nearly meet at the northwest corner. The chief entrance is the Black Gate, the Morannon, set in a deep cleft and guarded by the Towers of the Teeth. To the west, the pass of Cirith Ungol above Minas Morgul offers a secret and terrible way in, guarded by the great spider Shelob.
Within the mountain walls lies the plateau of Gorgoroth, a blasted waste of ash and slag, from which rises Mount Doom (Orodruin). Beyond it stretches the inner land of Nurn around the bitter sea of Núrnen, where slaves toil to feed Sauron's armies. Barad-dûr, the Dark Tower, stands upon a spur of the Ash Mountains, overlooking all.
History
Sauron chose Mordor as his stronghold in the Second Age because of its natural defenses and the fire of Mount Doom, where he forged the One Ring. From Barad-dûr he warred against the Elves and the Numenoreans and the realms in exile. He was overthrown when the Last Alliance of Elves and Men besieged Barad-dûr and Isildur cut the Ring from his hand, but his spirit endured. In the Third Age Sauron returned to Mordor and rebuilt his power, gathering orcs, trolls, and the armies of his servants for renewed war.
In the story
Frodo and Sam, guided and betrayed by Gollum, enter Mordor by the pass of Cirith Ungol and cross the ashen waste of Gorgoroth to Mount Doom. While the armies of the West draw Sauron's gaze and his forces to the Black Gate in the Battle of the Morannon, the hobbits reach the Cracks of Doom, and the Ring is at last destroyed. With its unmaking, Sauron's power is broken forever, Barad-dûr falls, and the land of Mordor is cast down.