Forward
(I shall keep this brief, as I know a long-winded glorified Author's Note is not what you're here for.)
Barad-dûr has always fascinated me, and I spent long hours trying figure out how high the tower was, and far the Eye could actually see (if we're using Peter Jackson's movie fore reference) then about eighty miles or so, but if we're using the books then a whole heck of a lot farther than that. (How I came to these conclusions will be discussed in a later chapter. There was math involved, and it hurt.)
And I will try to answer other questions besides. How Barad-dûr had access to water, or how the people of Sauron's Tower might have been adept farmers.
I will also be taking requests. So if you have any questions please shoot them forward, and I will try to answer them.
A fair warning. This will not be receiving regular updates, as I have other things going on. But I do intend to continue this for some time, so please add it to your alerts, and try not to freak-out if it falls to the bottom of that list. But do feel free to PM me as often as you wish, to nag me. ;)
(Nagging works, more often than not. And I don't mind some light pestering.)
I would also like to point out that this is not the most organized of pieces. I just answer questions as they come and explore ideas as I think of them. Much of what I put here, while having a basis within the book lore, will likely deviate once things get rolling. That said, I will be taking a look at Peter Jackson's rendition of the tower, as well as the version created by Rankin and Bass (mostly for the fun of it.)
This is an exploratory piece, written mainly for fun, and because world building can be and is a struggle, especially in regards to a place so mysterious. Everything here is up to debate (and I love geeking over stuff like this so by all means share your ideas ;) ) so if you're thinking of writing a fic that takes place in the black heart of Mordor, you are of course, free to use and anything you wish to from here.
And I own nothing. Some of the questions are mine, some have been asked by others. These are my answers to them, and while I try to be mathematically, magically, and architecturally accurate, I must inform you that I am no mathematician (otherwise I'd be digging up dinos in Mongolia) nor am I magician, and I'm certainly not an architect, and while I can claim to have some personal knowledge of hydroponic garden and farming, I am a hobbyist, not an expert. And for the record I claim no ownership of anything within these chapters.
So moving forward, as the title suggests what do we really know about Tolkien's Tower?
Well to start, Barad-dûr is described a massive place with courthouses and prisons the size of hills. And it's higher towers are lost amid the clouds. A darkness even greater than the cloouds (I imagine to be a bit like Ungoliant's un-light) veils the tower, making its exact details difficult to see.
It's described as having an utmost tower, so presumably there were multiple towers.
According to the LOTR Wiki, the structure stood about 1,400 meters or 4,593 feet tall. So just shy of a mile in height. Is this accurate? I have no idea, since a lot of people have theories about this, but personally I like the idea of it being absurdly tall. So in TYW and any other fics I've written I'll just straight up tell you it's a mile tall, exactly, because anti-entropy, chaos-hating Sauron ain't got no time for approximations. This being said, there are several answers to this question and all shall be examined under the proverbial microscope later.
So what else do we know from canon?
Well it was built on the southern spur of Ered Lithui in the norther part of Gorgoroth, which I've taken to imply, the foundation of the tower is the foot of a mountain. Sauron chopped down a mountain, and replaced it with a tower. And carrying my theory further, I believe the stone from the mountain was used to build the tower, but I'll go into my head-canon about the tower's actual construction later.
The tower was roughly 30 miles from Mount Doom, and 100 miles from the Black Gate.
From the steel gate of the tower, a causeway ran out to the plain of Gorgoroth, across a mighty bridge, that somewhere I read was a few miles long…uh I need to cite my resources. (That'd be helpful. Right?) The bridge in question could have been as short as three miles or as long as eight. Eight I believe being the more realistic figure. (Again having my sources at hand would be a benefit, rather than trying to recall all this from memory, at three in the morning, but again this will be another matter dealt with later in greater detail.)
We also know lava was channelled across the plain to the tower, quite likely used in the foundries and forges. (The Peter Jackson movies get this right, as well as the bridge.)
The tower is described as hard, cold, and made of iron, and adamant. Adamant typically refers to diamonds…but it's unlikely the tower was made of literal diamond. That said there are black diamonds. So you know... that would actually be freakishly awesome. Why settled for the polished marble floors when instead you can the tower's interior shimmer like an all-consuming pool of liquid obsidian. (Please somebody adopt the idea of a black diamond Barad-dûr. This needs to be a thing! And then kindly link me your fanfic so I can read it. Thanks!)
But aside from delightful fantasy of black diamond towers, adamant mostly means, 'hard and unbreakable.'
The topmost tower is most likely where Sauron dwelt, but even if he didn't have his abode a mile in the sky, the Window of the Eye was certainly located there.
Regrettably there is little more to glean from source material beyond these delightful tidbits, Tolkein was purposely vague when describing the tower. But this is where I shall step in and try to fill in the gaps.