What are the Two Towers?

[The Saucepan Man]

Well, it appears that Tolkien himself was not wholly decided on the issue and preferred that it be left ambiguous. If pressed, however, it seems that he would have nominated Orthanc and the Tower of Cirith Ungol, although his original jacket design depicted Orthanc and Minas Morgul.

Here are some illuminating extracts from The Letters on this issue:

The Two Towers gets as near as possible to finding a title to cover the widely divergent Books 3 and 4; and can be left ambiguous — it might refer to Isengard and Barad-dûr, or to Minas Tirith and
B[arad-dûr]; or Isengard and Cirith Ungol.

Letter #140 (to Rayner Unwin, dated 17 August 1953)

I am not really happy about the title 'the Two Towers'. It must if there is any real reference in it to Vol II refer to Orthanc and The Tower of Cirith Ungol. But since there is so much made of the basic opposition of the Dark Tower and Minas Tirith, that seems very misleading.

Letter #143 (to Rayner Unwin, dated 22 January 1954)

In the editorial notes, it states:

In his original design for the jacket of The Two Towers the towers are certainly Orthanc and Minas Morgul ... Minas Morgul is a white tower, with a thin waning moon above it, in reference to it's original name, Minas Ithil, the Tower of the Rising Moon.

The first of the quotes above also touches upon the symbolic nature of the title pointed out by Firefoot.

Since I do not have my books with me, the quotes above are provided courtesy of Diamond18's post in the second of the threads linked to below, all of which provide further thoughts on this point:

Two Towers?

Which towers are the Two Towers?

Towers

[Boromir88]

While it appears, as SpM points out, that Tolkien wasn't sure what he ment by the Two Towers, we could still form our guesses. I would say it's Isengard and Barad-dur.

If we look in The Breaking of the Fellowship, when Frodo is upon Amon Hen, there are places mentioned. Isengard, Minas Tirith, Minas Morgul, and Barad-dur. I don't want to quote the whole thing, since it's like a page, so it will only be the parts I'm looking at. If you wish to see the whole thing, well you know where it is.

After part about the Misty Mountains, and Anduin, Isengard is mentioned...

Westward he looked and saw the broad pastures of Rohan; and Orthanc, the pinnacle of Isengard, like a black spike.

Then turning south again he beheld Minas Tirith. Far away it seemed, and beautiful: white walled, many-towered, proud and fair upon its mountain-seat, its battlements glittered with steel, and its turrets were bright with many banners.

But against Minas Tirith was set another fortress, greater and more strong. Thither, eastward, unwilling his eye was drawn. It passed the ruined bridges of Osgiliath, the grinning gates of Minas Morgul, and the haunted Mountains,....

Then at last his gaze was held: wall upon wall, battlement upon battlement, black, immeasurably strong, mountain of iron, gate of steel, tower of adamant, he saw it: Barad-dur, Fortress of Sauron.

These are 4 of the places being discusses that could be The "Two" Towers. Seeing that it is "Two" Towers, I think that excludes Minas Tirith, since it is "many-towered." Minas Morgul is compared to Minas Tirith, as being even greater and stronger, so that excludes Minas Morgul.

Barad-dur, the "tower" of adament, and Orthanc, the "pinnacle" of Isengard. Pinnacle=Tower. That's just my argument for the story, since Tolkien wasn't sure, and has a wide range of possibilities, we won't know, this is just how I think of it.

[Estelyn Telcontar]

It is interesting to note that Peter Jackson's interpretation of the Two Towers in the movie(s) makes them Orthanc and Barad-Dûr, naming the alliance between the two towers as the reason.

[Eomer of the Rohirrim]

It is funny how the book is called The Two Towers, despite the fact that the reader is usually up to his ascots in Towers.

I think Orthanc and Cirith Ungol. The journeys in Book 3 lead to Orthanc. The journey in Book 4 leads to Cirith Ungol. Those are the two towers where our heroes end up. The Two Towers as a single book is centred around those progressions.

[Legolas]

It is interesting to note that Peter Jackson's interpretation of the Two Towers in the movie(s) makes them Orthanc and Barad-Dûr, naming the alliance between the two towers as the reason.

I've always thought of the two as Orthanc and Barad-Dûr.

[Lolidir]

i did a paper on Tolkien last year and during my research i remember reading something about this, although i have no idea where or exactly what it said. it was just explaining that as SpM said Tolkien didnt really have an idea for which "Two" towers it refered to. if i remember right he needed a title and that is what he came up with.

I guess its up to you which two you choose to think about. as for my opinion i have always thought of Minas Tirith and Cirith Ungol wich used to be the twin city so-to-speak of Minas Tirith.

[Neithan]

When I read the books I get the strong impression that it is Orthanc and Barad-Dûr. A large part of The Two Towers focuses mainly on Orthanc. When Orthanc is defeated their attention is turned to the bigger threat, Barad-Dûr.
There is a comparison going on between Saruman and Sauron. Saruman is trying to immitate Barad-Dûr with Orthanc, but he can not compare. Though Saruman was the main focus of most of The Two Towers and there is a definate feeling of victory when he is defeated, Tolkien soon reminds us that this was just the first round. There is still a greater enemy (second tower) to think of. Thus The Two Towers not Orthanc or Saruman's Tower.
Anyway that was my interpretation.