IMHO - definitely not urban. Well not for games like OA anyway. But it's always a matter of preference and everyone has a different opinion.
I've always liked easy-to-reach powerups in plain sight (like the quad in oa_shine) so everyone has to compete for it when it appears. Several players rushing from every corner of the map to be there when it respawns is a lot of fun.
Pitfalls can be annoying if there are too many of them, but a well placed pit can be very entertaining (newbies going for the quad in czest1dm
).
I also think hidden rooms and passages are a good touch every once in a while (like in kaos2 and oa_dm2).