Grab the London A-Z, or the map book for any city.  Tear it in half lengthwise through the binding (or cut it on a bandsaw) being careful to tear as many pages as possible.  Draw and examine what you see.  Rebuild the city to match the picture now at hand.  One street tears away so that the traveler’s next step is to a much lower elevation across town.  A building is cut off and the open rooms face a slice of park and across it, more torn away buildings.  And there are the white places.  Parts of the map have been so torn away that nothing exists there anymore.  What is the new city like?