If you don't mind the ancient aesthetics, there's always
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. The good part? It exports as SVG, so you can customize your map in Illustrator/Inkscape as much as you want.
No isometry out of the box, so that's probably not what you are looking for.
I know that there are ways to "3D" real city maps, so you can steal one from OpenStreetMaps. I saw it done with Berlin, but I can't remember what tools are needed. One way passed from HTML 5.0 (IIRC, so probably not) and one from Blender.
Or you can, well, just build your city directly in Blender/Daz/whatever: there are tons of "city blocks" assets.