It should be Orthanc and Barad-Dur...as the 2nd book is about the union between these two towers...
After all, only two towers refer to any political structure in the books, Barad-dur, the bad guys...and Orthanc...the good guys...the white city represents Gondor, and the old days...and so on...nothing else actually represents any political structure.
Orthanc is supposed to represent the side of good, but that's never really gone into...
And I'm sure the Director who has researched this FAR longer than any of us...would not make a mistake like that...he is careful what he has to leave out and change....and I'm sure..heartbroken.
*EDIT* Orthanc can also represent the folly of power...Orthanc is after all, Saruman's alter-ego.
Notice all the wizards run around in the wilds like animals...Saruman wasn't content with this, he established a huge fortress, and gathered workers to serve him from all around...this was of course while everyone thought he was the uber-good guy...
But the Gods knew what they were doing putting him into power...and after all, Saruman did ruin Sauron's plans.