I drove from Toronto to Detroit once for a Jays game.  On the way back we took a wrong turn and ended up in a really nasty looking area.  We locked the doors, rolled up the windows and didn't ever come to a full stop until we got outta there.  Freaked us both out.
But I think the title of this thread is not fair to Detroit.  There is alot worse in the world today and although I didn't see them I'm sure there are some nice parts of town.