Civilization began with agriculture. Towns came second, and then came cities. The farmer made it all possible.
In the Western world, the only remaining savages are most commonly found in the city, where the prey is more plentiful.
Too great a local population density is a bad idea, for a great many reasons. Especially these days. On 9/11, two flying bombs took out almost three thousand souls who ahppened to be in close physical proximity to one another. A third crashed in rural Pennsylvania, killing far fewer.
Decentralization is the wave of the future. It's just a matter of getting that last mile problem completely licked. We'll still need port cities, but no one will have to live in them anymore. We'll just have waldoes for dockworkers.