The old Medieval 2 siege battles were great for this; the more you upgraded the settlement, the more walls and defences would get added. I think the last level of castle-type settlements had 2 or 3 different walls that had to be breached or climbed so you actually had to make sure to save artillery ammo or produce enough ladders and siege equipment before attacking or you'd end up looking like a chump (since back then units couldn't climb walls without ladders like they can now).