I think you are confusing nature with economic vitality. There needs to be economic value inherent in a location for a city to thrive. Having grass and water doesn't mean much at all in this regard. You need things like natural harbors, navigable river ways or mine-able resources.
Pretty much all the good spots for cities have already been claimed, hundreds of years or even millennia ago. These are the spots people live in, and the spots people want to live in (as evidenced by ever increasing cost to live there).
> Having grass and water doesn't mean much at all in this regard. You need things like natural harbors, navigable river ways or mine-able resources.
Harbors? No. Trains and airplanes exist.
River ways? Los Angeles and California have demonstrated, with the LA river, that rivers can be constructed. Also, trains and airplanes exist. Wanna complain about no water? Well that's where land revitalization comes in.
Mine-able resources? Perhaps. There are lots (!) of resources in deserts that aren't mined. I also argue that food is basically a mine-able resource. I also argue that many resources can be imported instead. I also argue that plenty of people can work remotely without ever working a field or a mine.
Pretty much all the good spots for cities have already been claimed, hundreds of years or even millennia ago. These are the spots people live in, and the spots people want to live in (as evidenced by ever increasing cost to live there).