Well That was most basic example i could think of in 5 seconds '-' I meant more like, Interactive terrain? I guess thats good way to call it. And going back to this circle with archers, such things could be reward for creative thinking. For example, there's no real quest for it but circle exists on hill. Road to hill is blocked by trees, and you are unable to see what is on top of this hill. Some players would just ignore it, some would cut through the woods and see their little reward that gives them Major/Minor adventage. Of course creating terrain with addition of such small rewards could be a bit annoying to make '-'.