Well, about the city, I'd go with somewhere with less deep history in it, an urban melting pot that had only sprawled not earlier than 1-2 centuries before the start point. Immigrants participated actively in its shaping and even the question of "where do you come from" would commonly get the answer of "here" regardless on the ethnicities of the one being asked. Economic gap was prominent so there could also be some noticeable portions of both skyscrapers and ghetto.

I'm quite open on how segregated it could be, ranging from nonexistent, to like having stereotypical gangs based on ethnic groups or other kind of groupings, to even having separated communities with their own languages that one living in it might get inspired to create a conlang in order to unite the people (yea, I know Zamenhof).

Particularly for my character, maybe the City needs a Chinatown.