In one sense, a city is a place where we have decided to put people closer together than normal.
This crowd of people creates problems, clearly it's impossible to have enough farmland within walking distance to feed a city. So we bring food in and ship waste out.
The opportunities created by this crowd are staggering, and we have entire services like Yelp, Meetup, and and Google Maps dedicated to collecting and organizing them. This abundance is magical for anyone who thrives on connections with other humans.