I haven't read all the books concerning the Great War and everything related to it, I don't think, and I suppose none of them really go into the specifics of the damage caused to the city when it was taken.

I would like to know what sort of damage you expect to have occurred. As in, which of the major buildings/statues/etc from Oblivion do you think would still be standing by the time Skyrim's story line begins?

I am on the second draft of the first entries for my journal and I want to talk about my character's stop in the Imperial City on her way to Skyrim but I am not sure what state the city would most likely be in.

Obviously if you can link me to an in-game book I might have missed, that would be very much appreciated.

Dexion Evicus mentions that the W-G Tower had sustained some damage when the Imperial City was occupied by Aldmeri forces during the Great War.

There are no specifics as far as I can tell, though I believe White-Gold sustained damage from...well, something. I assume that its probably general pillaging and pilfering going on, we really don't get a sense of scale as to what really transpired.