Whoops, I blew it, sorry <sheepish look on red face>. Shouldn’t have been in such a hurry to post the first response.
On second thought, Minas Tirith wasn’t introduced into the narrative until Book Five in The Return of the King. The two towers that figured large in The Two Towers were indeed Orthanc and Barad-Dûr.
Glad we helped you out there, toad.
It makes a little more sense if you think about how the book is structured. The first half is pretty heavy on Orthanc, and the second part ends with Frodo et al having just passed Minas Morgul.
I often thought, however, that Minas Morgul was inadequately developed in the books. And Barad-dur is not really developed at all. I have a very vague mental image of both places.
Many thanks are due thee, fair tourbot; this should settle toad’s question to everyone’s satisfaction. You can pretty much name any two towers and you’ll have as good a chance as anyone else of being right.
The link is correct. The Tower of Orthanc, from which Saruman directed the events of Book 3, and the Tower of Cirith Ungol (“Pass of the Spider”) where Frodo wound up imprisoned at the end of Book 4.