I looks good so far...but I MUST say something about those bridges.Most spans, if not all, are straight from first anchor point to the next.Both of then curve away from the direct line quite noticeably. As the map is a top-down view, they should be straight. If the map was viewed at an angle then I could say that the bridges were arched (and quite a bit at that) but from the rest of the map I would not say that is the case. In a top-down map, if you want to show an arched bridge, you would need to use a shadow to show that it is not flat.
Out of curiositywhat are you planning for that space just upper left from center?
Like I said before, I like so far. The river really stands out.