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|Place from J. R. R. Tolkien's legendarium|
|Other names||Lugbúrz (Black Speech)|
|Description||Tower of Sauron|
|Lifespan||S.A. c. 1600– T.A. 3019|
Barad-dûr (Sindarin "Dark Tower", sometimes given as The Barad-dûr (Lugbúrz in Black Speech)) is the fortress of Sauron in the heart of the black land of Mordor and close to Mount Doom in the fantasy world of J. R. R. Tolkien's The Lord of the Rings. The Eye of Sauron kept watch over Middle-earth from its highest tower.
Barad-dûr was built by Sauron, the Dark Lord of Mordor, with the power of the One Ring, during the Second Age. The building took six hundred years to complete; it was the greatest fortress ever built since the Fall of Angband, and much of Sauron's personal power went into it.
Barad-dûr was besieged for seven years by the Last Alliance of Elves and Men and was levelled after Sauron's defeat at the end of the Second Age, but because it was created using the power of the One Ring, its foundations could not be destroyed completely unless the Ring itself was destroyed. Isildur cut the Ring from Sauron's hand but refused to destroy it, so the Tower was quickly rebuilt when Sauron returned to Mordor thousands of years later, in T.A. 2951.
The Dark Tower was described as existing on a massive scale so large it was almost surreal, although Tolkien does not provide much detail beyond its size and immense strength. Since it had a "topmost tower" it presumably had multiple towers. It is otherwise described as dark and surrounded in shadow, so that it could not be clearly seen.
- "..rising black, blacker and darker than the vast shades amid which it stood, the cruel pinnacles and iron crown of the topmost tower of Barad-dûr..."
In his vision at Amon Hen, Frodo Baggins perceived the immense tower as "wall upon wall, battlement upon battlement, black, immeasurably strong, mountain of iron, gate of steel, tower of adamant...Barad-dûr, Fortress of Sauron".
There was an "immeasurably high" look-out post, "the Window of the Eye in Sauron’s shadow-mantled fortress", said to face Mount Doom. In this window, Frodo and Sam had a terrible glimpse of the Eye of Sauron.
There is a drawing by Tolkien that he titled "Barad-dûr"; since he did not publish it during his lifetime, it is unclear how close the drawing is to his mature vision of the tower. The picture shows only the left edge of the lower part of a structure that seems to be constructed of immense masonry blocks of some greenish-grey stone. The few existing windows are small and either dark or lighted dark red; one is clearly barred. One high, thin vertical spire is visible in the background. The whole building seems to stand on top of a large monolithic rock with almost vertical edges and a relatively flat top. A narrow stone bridge leads across the chasm to the single visible door, through which flames can be seen inside the tower. An erupting volcano (presumably Mount Doom) can be seen in the background, a lava stream flowing from there past the side of the monolithic rock.
Depiction in adaptations 
The Lord of the Rings: The Return of the King also shows Barad-dûr as clearly visible from the Black Gate of Mordor. Even granting its enormous size, it was 100 miles away and east of the Gate, and behind the inner mountain ridges of Udûn, so Aragorn's army could not have seen it. It is also shown in front of Mount Doom, but when looking from the gate as shown in the maps of Middle-earth, Barad-dûr is somewhat behind Mount Doom (although some of the maps of Mordor in the film are altered so that Barad-dûr is not blocked by the mountains of Udûn.) In the Black Gate scene, having Barad-dûr visible from the Gate means that the army can see the Eye of Sauron staring at them. This was done because of the deleted "Aragorn vs Sauron" scene. Originally there would be a "blinding light" and Aragorn would see Annatar (Sauron's pleasant appearance that he had used to deceive the Elves in the Second Age), who would then become Sauron and attack. However, the filmmakers decided that this deviated too far from the books, so instead the blinding light scenes were used to depict a "staring contest" between Aragorn and the Eye of Sauron.
Again another deleted scene in the extended edition of The Return of the King appears to reinforce this view, showing Sauron standing atop his tower and briefly being observed by Aragorn.
- Tolkien, J. R. R. (1955), The Return of the King, The Lord of the Rings, Boston: Houghton Mifflin (published 1987), ISBN 0-395-08256-0
- "Encyclopaedia of Arda Barad-dûr article".