You're seeing vestiges of the VWD buildings that Bethesda puts behind the city walls. At least from what it looks like. It shouldn't be happening. Are you using Open Cities?
Vestiges of the VWD buildings? 2 foots close to them? So it's more strange than I thought.
And no, I don't use Open Cities. The only texture replacement for city walls that I can think of are those from UOP. What the hell could have happened, do you have any ideas? The only "strange" thing I made was to merge all the UL in one esp, and all the resources has been packed in one bsa. Then I edited the masterlist to avoid colfilcts and merged all my UL-related patches in another esp.. So far as I can see UL are working well. But I don't see how this could be related to my issue, since we are speaking of a vanilla Oblivion texture... I don't think vanilla replacement are included in the UL....
I will try to disable the UL, though. In the meantime, do you have other suggestion? And thanks in advance for your help and disponibility!