What lies in Mordor besides Mount Doom and Barad-dur?

Question

Mordor is so big on the Middle-earth map, but the only significant structures in there are the Eye of Sauron and Mount Doom. Since Mordor is so heavily guarded, I would think that there would be more than a castle and a giant volcano that hardly anyone uses anymore. I know about orc-breeding grounds, but I'm guessing that is only in the small corner by the Black Gate. I see that there is a sea on the bottom corner. Since Mordor is a desert, I would think it would be a valuable resource. Is there anything over by there? And in the west, is there really NOTHING there?

Answer 1

Mordor has more than just a mountain and a tower. As you can see from Tolkien's annotated map (bottom), the Mountain of Doom and Tower of Sauron merely make up a small corner of Mordor, namely the Plateau of Gorgoroth. In addition to the Plateau (sometimes named the 'Plains'), Mordor also consists of Nurn, which is the fertile land surrounding the Sea of Nurnen that fed Sauron's armies during the Lord of the Rings and the years before. There are also two major mountain ranges, the Mountains of Ash bordering northern Mordor and the Mountains of Shadow defining Mordor’s western and southern borders. These two ranges come together in the north west to form the dale of Udûn, a large strategic valley important in the books and movies, laying beyond the Black Gate, which is the main entryway into Mordor, and before the Isenmouthe, the inner gateway and another fortress guarding Mordor. Various roads and paths, major and minor, as well as caverns run throughout the ranges and lands. Below is a list of the things that lie within Mordor.

Durthang

A castle at the point where the Ephel Duath meets the hills of 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}

The Tower of 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}

Towers of the Teeth

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.

The 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.

Hills of the Teeth

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}

Slag-Hills of the 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}

Sea of 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}

Black Trough of the 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}

The Road from Durthang to 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}

Sauron's Road

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

On top of the above in the quotes there exist other caves, holds, armouries, streams and fields around the sea of Nurnen all of which lie within Mordor. A lot of the details come in the final few chapters of Sam and Frodo's tale, and really shows the descriptive nature of Tolkien's writing. Few details are added in the Silmarillion and later writings.

Answer 2

Mordor isn’t a complete desert. The southern part has fields producing food for Sauron’s armies (bold added):

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

There are armouries and forts in the northern range (bold added):

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

The north-west includes Durthang, mentioned in M. A. Golding's answer, along with other orc-holds (bold added):

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

Answer 3

The Eye of Sauron isn't a structure, it is a metaphor for Sauron's watchfulness and gathering of information by natural and magical methods.

Mount Doom isn't a structure, it is a geological feature.

The main structure in northwest Mordor is the Dark Tower, Barad-Dur, a mighty fortress with no doubt a large population living in it.

The northwestern most of Mordor is the plain of Udun, guarded on the north by the Black Gate, the Morannon, an do the the south by another wall and gate, the Isenmouthe. The Plateau of Gorgoroth occupied the rest of northwest Mordor, and was desolate because of the volcanic activity of Mount Doom. The Dark Tower, Sauron's capital, was in Gorgoroth.

Southern Mordor was Nurn, which contained the Sea of Nurnen, fed by several rivers. There were vast farms in Nurn worked by Sauron's slaves to feed his armies. So no doubt there were many slave barracks, barns, and other farm buildings in Nurn.

The dry plain of Lithlad was east of Gorgoroth and north of Nurn.

https://en.wikipedia.org/wiki/Mordor1

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

http://tolkiengateway.net/wiki/Nurn2

Any large inhabited region like Mordor is bound to have many hundreds and thousands of buildings and other structures. Even deserts will have some structures build by man.

In LOTR, Frodo and Sam see Mordor structures such as:

1) The city of Minas morgul, which is technically outside of Mordor in Ithilen,

2) The Morannon Gate of Mordor,

3) The Isenmouthe wall and gate,

4) The Tower of Cirith Ungol,

5) And in the distance the dark Tower, Barad-Dur.

And there is mention of the fortress of Durthang which I don't think that Frodo or Sam ever glimpses.

Thus there are several structures in the desolate and mostly uninhabited northwest Mordor, and there should be many more in the populated region of Nurn.