[Feature Request] Display city (area) boundaries

[ysmartin]

It would be nice to have the option to also render the boundary of the city (or area).
Sometimes, roads cross the boundary and go far out of it. More often, there are patches near the boundary where there isn't any road, and theres a "bite" in the shape of the city (or area). In either case, having option to have the boundary explicitly drawn would be useful.