Mordor tem mais do que apenas uma montanha e uma torre. Como você pode ver no mapa anotado de Tolkien (embaixo), a Montanha da Perdição e a Torre de Sauron apenas formam um pequeno canto de Mordor, a saber, o Planalto de Gorgoroth . Além do Planalto (às vezes chamado de 'Planícies'), Mordor também consiste em Nurn, que é a terra fértil em torno do Mar de Nurnen que alimentou os exércitos de Sauron durante o Senhor dos Anéis e nos anos anteriores. Há também duas cadeias montanhosas principais, as Montanhas de Freixo, que fazem fronteira com o norte de Mordor e as Montanhas da Sombra, definindo as fronteiras oeste e sul de Mordor. Essas duas faixas se reúnem no noroeste para formar o vale de Udûn, um grande vale estratégico importante nos livros e filmes, situado além do Portão Negro, que é a entrada principal de Mordor, e antes do Isenmouthe, o portal interno e outra fortaleza guardando Mordor. Várias estradas e caminhos, maiores e menores, bem como cavernas percorrem as faixas e terras. Abaixo está uma lista das coisas que estão dentro de Mordor.

Durthang

Um castelo no ponto onde o Ephel Duath encontra as colinas de Udûn

A few miles north, high up in the angle where the western spur branched away from the main range, stood the old castle of Durthang, now one of the many orc-holds that clustered about the dale of Udûn. A road, already visible in the growing light, came winding down from it, until only a mile or two from where the hobbits lay it turned east and ran along a shelf cut in the side of the spur, and so went down into the plain, and on to the Isenmouthe.
_{The Return of the King - Book 6, Chapter 2: The Land of Shadow}

Minas Morgul

Upon the further side, some way within the valley's arms high on a rocky seat upon the black knees of the Ephel Dúath, stood the walls and tower of Minas Morgul. All was dark about it, earth and sky, but it was lit with light. Not the imprisoned moonlight welling through the marble walls of Minas Ithil long ago, Tower of the Moon, fair and radiant in the hollow of the hills. Paler indeed than the moon ailing in some slow eclipse was the light of it now, wavering and blowing like a noisome exhalation of decay, a corpse-light, a light that illuminated nothing.
_{The Two Towers - Book IV, Chapter 8: The Stairs of Cirith Ungol}

A Torre de Cirith Ungol

...he could see the Tower of Cirith Ungol in all its strength. The horn that he had seen from the other side was only its topmost turret. Its eastern face stood up in three great tiers from a shelf in the mountain-wall far below; its back was to a great cliff behind, from which it jutted out in pointed bastions, one above the other, diminishing as they rose, with sheer sides of cunning masonry that looked north-east and south-east. About the lowest tier, two hundred feet below where Sam now stood, there was a battlemented wall enclosing a narrow court. Its gate, upon the near south-eastern side, opened on a broad road, the outer parapet of which ran upon the brink of a precipice, until it turned southward and went winding down into the darkness to join the road that came over the Morgul Pass.
_{Return of the King - Book VI, Chapter 1: The Tower of Cirith Ungol}

Torres dos Dentes

North amid their noisome pits lay the first of the great heaps and hills of slag and broken rock and blasted earth, the vomit of the maggot-folk of Mordor; but south and now near loomed the great rampart of Cirith Gorgor, and the Black Gate amidmost, and the two Towers of the Teeth tall and dark upon either side.

O Morannon

Across the mouth of the pass, from cliff to cliff, the Dark Lord had built a rampart of stone. In it there was a single gate of iron, and upon its battlement sentinels paced unceasingly. Beneath the hills on either side the rock was bored into a hundred caves and maggot-holes: there a host of orcs lurked, ready at a signal to issue forth like black ants going to war.
_{The Two Towers - Book IV, Chapter 3: The Black Gate is Closed}

Gorgoroth

As the light grew a little he saw to his surprise that what from a distance had seemed wide and featureless flats were in fact all broken and tumbled. Indeed the whole surface of the plains of Gorgoroth was pocked with great holes, as if, while it was still a waste of soft mud, it had been smitten with a shower of bolts and huge slingstones.
_{Return of the King - Book VI, Chapter 3: Mount Doom}

Lithlad

Upon the west of Mordor marched the gloomy range of Ephel Dúath..., and upon the north the broken peaks and barren ridges of Ered Lithui, grey as ash. But as these ranges ap­proached one another, being indeed but parts of one great wall about the mournful plains of Lithlad and of Gorgoroth..., they swung out long arms northward....
_{The Two Towers - Book 4, Chapter 3: The Black Gate Is Closed}

Cirith Gorgor

But as these ranges approached one another..., they swung out long arms northward; and between these arms there was a deep defile. This was Cirith Gorgor, the Haunted Pass, the entrance to the land of the Enemy. High cliffs lowered upon either side, and thrust forward from its mouth were two sheer hills, black-boned and bare. Upon them stood the Teeth of Mordor, two towers strong and tall....
_{The Two Towers - Book 4, Chapter 3: The Black Gate Is Closed}

Ephel Dúath

Upon the west of Mordor marched the gloomy range of Ephel Dúath, the Mountains of Shadow...
_ibid.

Ered Lithui

...and upon the north the broken peaks and barren ridges of Ered Lithui, grey as ash.
_ibid.

Colina dos Dentes

Down from the hills on either side of the Morannon poured Orcs innumerable.
_{The Return of the King: Book 5, Chapter 10: The Black Gate Opens}

Morgai

Hard and cruel and bitter was the land that met his gaze. Before his feet the highest ridge of the Ephel Dúath fell steeply in great cliffs down into a dark trough, on the further side of which there rose another ridge, much lower, its edge notched and jagged with crags like fangs that stood out black against the red light behind them: it was the grim Morgai, the inner ring of the fences of the land...
_{The Return of the King - Book 6, Chapter 1: The Tower of Cirith Ungol}

Colinas de Escória do Morannon

Frodo reaches the slag-mounds on the edge of the Desolation of the Morannon.

The Host is surrounded on the Slag-hills.
_{The Lord of the Rings, Appendix B, The Tale of Years: The Third Age}

Morgulduin

Frodo shuddered ... the sound of the water seemed cold and cruel: the voice of Morgulduin, the polluted stream that flowed from the Valley of the Wraiths.
_{The Two Towers - Book 4, Chapter 7: Journey to the Cross-roads}

Mar de Nurnen

It is described as "the bitter inland sea of Núrnen" in TTT The Black Gate is Closed. It is fed by 4 rivers which are unnamed, two from the Ephel Dúath and two from the Ered Lithui (Ash Mountains). As it has no outlet to the sea, it loses water only by evaporation, thereby concentrating the dissolved minerals. This should result in a body of water similar to the Dead Sea.
_{Unfinished Tales}

Isenmouthe

The trough between the mountains and the Morgai had steadily dwindled as it climbed upwards, and the inner ridge was now no more than a shelf in the steep faces of the Ephel Dúath; but to the east it fell as sheerly as ever down into Gorgoroth. Ahead the water-course came to an end in broken steps of rock; for out from the main range there sprang a high barren spur, thrusting eastward like a wall. To meet it there stretched out from the grey and misty northern range of Ered Lithui a long jutting arm; and between the ends there was a narrow gap: Carach Angren, the Isenmouthe, beyond which lay the deep dale of Udûn.
_{The Return of the King - Book 6, Chapter 2: The Land of Shadow}

Calha Negra do Morgai

Out of a gully on the left, so sharp and narrow that it looked as if the black cliff had been cloven by some huge axe, water came dripping down: the last remains, maybe, of some sweet rain gathered from sunlit seas, but ill-fated to fall at last upon the walls of the Black Land and wander fruitless down into the dust. Here it came out of the rock in a little falling streamlet, and flowed across the path, and turning south ran away swiftly to be lost among the dead stones.
_{The Return of the King - Book 6, Chapter 2: The Land of Shadow}

Udûn

To meet [a spur of the Ephel Dúath] there stretched out from the grey and misty northern range of Ered Lithui a long jutting arm; and between the ends there was a narrow gap: Carach Angren, the Isenmouthe, beyond which lay the deep dale of Udûn. In that dale behind the Black Gate were the tunnels and deep armouries that the servants of Mordor had made for the defence of the Black Gate of their land; and there now their Lord was gathering in haste great forces to meet the onslaught of the Captains of the West.
_{The Return of the King - Book 6, Chapter 2: The Land of Shadow}

A estrada de Durthang para Udûn

A road, already visible in the growing light, came winding down from it, until only a mile or two from where the hobbits lay it turned east and ran along a shelf cut in the side of the spur, and so went down into the plain, and on to the Isenmouthe. ...
_{The Return of the King - Book 6, Chapter 2: The Land of Shadow}

Estrada de Sauron

He did not know it, but he was looking at Sauron's Road from Barad-dûr to the Sammath Naur, the Chambers of Fire. Out from the Dark Tower's huge western gate it came over a deep abyss by a vast bridge of iron, and then passing into the plain it ran for a league between two smoking chasms, and so reached a long sloping causeway that led up on to the Mountain's eastern side.
The Return of the King - Book 6, Chapter 3: Mount Doom

Além das citações acima, existem outras cavernas, porões, arsenais, riachos e campos ao redor do mar de Nurnen, todos dentro de Mordor. Muitos detalhes vêm nos últimos capítulos do conto de Sam e Frodo, e realmente mostram a natureza descritiva da escrita de Tolkien. Poucos detalhes são adicionados no Silmarillion e em escritos posteriores.

    

Mordor não é um deserto completo. A parte sul tem campos de produção de alimentos para os exércitos de Sauron (negrito adicionado):

Neither he [Sam] nor Frodo knew anything of the great slave-worked fields away south in this wide realm, beyond the fumes of the Mountain by the dark sad waters of Lake Núrnen; nor of the great roads that ran away east and south to tributary lands, from which the soldiers of the Tower brought long waggon-trains of goods and booty and fresh slaves. Here in the northward regions were the mines and forges, and the musterings of long-planned war; and here the Dark Power, moving its armies like pieces on the board, was gathering them together.

The Lord of The Rings (The Return of the King, Book 6). Chapter 2. The Land of Shadow

Existem arsenais e fortalezas na faixa norte (negrito adicionado):

Carach Angren, the Isenmouthe, beyond which lay the deep dale of Udûn. In that dale behind the Morannon were the tunnels and deep armouries that the servants of Mordor had made for the defence of the Black Gate of their land; and there now their Lord was gathering in haste great forces to meet the onslaught of the Captains of the West. Upon the out-thrust spurs forts and towers were built, and watch-fires burned; and all across the gap an earth-wall had been raised, and a deep trench delved that could be crossed only by a single bridge.

Ibid

O noroeste inclui Durthang, mencionado na resposta de M. A. Golding, juntamente com outros orc-holds (negrito adicionado):

A few miles north, high up in the angle where the western spur branched away from the main range, stood the old castle of Durthang, now one of the many orc-holds that clustered about the dale of Udûn. A road, already visible in the growing light, came winding down from it, until only a mile or two from where the hobbits lay it turned east and ran along a shelf cut in the side of the spur, and so went down into the plain, and on to the Isenmouthe.

Ibid

    

O Olho de Sauron não é uma estrutura, é uma metáfora para a vigilância de Sauron e coleta de informações por métodos naturais e mágicos.

O Monte Doom não é uma estrutura, é um recurso geológico.

A estrutura principal no noroeste de Mordor é a Torre Negra, Barad-Dur, uma poderosa fortaleza sem dúvida uma grande população vivendo nela.

O noroeste da maior parte de Mordor é a planície de Udun, guardada ao norte pelo Portão Negro, o Morannon, e ao sul por outra parede e portão, o Isenmouthe. O Planalto de Gorgoroth ocupava o resto do noroeste de Mordor e estava desolado por causa da atividade vulcânica do Monte Doom. A Torre Negra, a capital de Sauron, ficava em Gorgoroth.

Mordor do Sul era Nurn, que continha o Mar de Nurnen, alimentado por vários rios. Havia vastas fazendas em Nurn, trabalhadas pelos escravos de Sauron, para alimentar seus exércitos. Então, sem dúvida, havia muitos quartéis de escravos, celeiros e outros edifícios agrícolas em Nurn.

A planície seca de Lithlad ficava a leste de Gorgoroth e ao norte de Nurn.

link 1

Nurn was the name given to the southern regions of Mordor, more fertile than Gorgoroth in the north, in which the great inland Sea of Núrnen lay.1 The people who inhabited Nurn were Men and there may have been prisoners of war there as well. These people were enslaved by Sauron, working the soil around the sea of Nurn to feed Sauron's armies.

After the War of the Ring, King Elessar liberated the peoples of Nurn and gave them the land as their own. The southern region of Nurn probably escaped the destruction caused in northern Mordor by the eruption of Mount Doom.2

link 2

Qualquer grande região habitada como Mordor provavelmente terá muitas centenas e milhares de edifícios e outras estruturas. Até os desertos terão algumas estruturas construídas pelo homem.

No LOTR, Frodo e Sam vêem estruturas de Mordor como:

1) A cidade de Minas morgul, que está tecnicamente fora de Mordor em Ithilen,

2) O Portão Morannon de Mordor,

3) A parede e portão de Isenmouthe,

4) A Torre de Cirith Ungol,

5) E à distância a Torre Negra, Barad-Dur.

E há menção da fortaleza de Durthang, que eu não acho que Frodo ou Sam vislumbrem.

Assim, existem várias estruturas no desolado e principalmente desabitado noroeste de Mordor, e deve haver muito mais na região povoada de Nurn.