I think the newer ones seem to blend better, but I was thinking about it... And its a smaller thing I guess, but up in the top corners of the map, you only have the "pattern/color" nothing else really to fill the space (if that makes sense) I checked on the Nile river on google maps, just to make sure my suggestion I was going to give had some credibility and when I looked, they had Hills/Mountain-ish looking terrain right up to the edge of the nile river. So having altering terrain leading up to the city or water could also be an idea to add to it (maybe even sand dunes).