stairs, you have added an extra edge in them, each step is made from 2 parts, least it looks that way, thats doubled the poly count, its a waste of polys,each step one part, bot two, just delete the extra edge its got in it.
Castle walls, they have the square set off on them, dont mind as an extra segment, but do the regular kind, as it adds loads of extra polys, fpsc runs as slow as hell, so one has to think of these things.
Also on the stairs, id extrude a railing/ledge, just create a edge on the step, extrude it then clean it up. that way they dont fall of the stairs.