I had only 2 weeks to meld an unfinished worldbuilding project into a GURPS setting and begin game play. I used quick and dirty methods for the battle maps.
here I do the same in the city design.

I used an infinite plain in vue enable sea level adjusted till I found a coast line I liked. then mixed and mashed airial images of cities (google earth, nasa etc.)
used layer masks and blending modes to place the features i liked onto the terrain.
photoshop paths and layerstyles to create the city walls.

quick and dirty city, with reasonable results. with more time the possibilities look pretty good.

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included standard map general locations etc, and a district division map(noble district, temple district, wharf district etc.)