Interior or exterior?

#1 Personally I would build the city buildings and the wall segments all as separate DIFs in Quark, then arrange them as needed in the mission editor. I would avoid the use of DTS for large collidable objects like a wall.

#2 Thanks for the response. For the wall segments, the wall around the city is fairly square. Should I break the wall into 4 segments, 1 for each side? Or if the walls or extraordinarily long should I break up those segments as well, like 2 segments for each side. Just trying to guage the optimal configuration for performance reasons.

#3 I do not think that the performance would be significantly different for 4 large segments or several smaller segments that were put together to form each side. I suppose it depends on how flexible/reusable you want the resources to be.

Personally I'd create some corner, wall, tower, and decoration pieces and mix and match them. That way you can make many differently shaped walled cities if you want. It also depends on if you want the inside of the walls (if they are hollow) to have uninterupted lighting throughout.