Honestly you’d be better giving John a real city. The problem with fictional cities is unless you put in the effort to build them up and make them feel “alive”, a lot of the time they can just become generic and boring. Gotham has a character all its own, but the other cities, Metropolis, Central, Coast, they struggle. If you anchor John in a real city you can draw on the culture of that place to shape his character without having to build said culture from scratch.