You would at least need: - A constant agrictultural surplus being able to support a city of this size. - A political system with some form of taxation and pro

You would at least need: - A constant agrictultural surplus being able to support a city of this size. - A political system with some form of taxation and probably a kind of military and/or police. - A construction and manufacturing industry. This is all really basic stuff for a modern society, but we only got here, because we built on giants.