Of course, places like Manhattan require a huge amount of supporting area. People just live there and work office jobs but everything they need is imported, and

Of course, places like Manhattan require a huge amount of supporting area. People just live there and work office jobs but everything they need is imported, and what they need to get rid of is exported. But you could look at something like Bangladesh that's more of a real country rather than a city and see how they do the density. Extreme fertility for farming and high poverty helps.