Most cities exist where they do for geographical reasons that have existed for longer than humans. Until the railroad (~200 years ago) you couldn't have a large city unless it had a good port as the only possible way to get enough food in to support a city was by boat. There are only limited places that support a great port so once humans start a city we can't abandon it. Today we could abandon NYC - the port itself would have to remain but everything else could move elsewhere (the port could not move elsewhere as most places don't have a way for ships to get in without massive ocean floor projects) - that won't happen because there is so much inertia of people already living there, but it could.

I don't know what the natives in Australia did. however I can report without looking that if they had the numbers to build cities they would be about where the current cities are.