Cities so big that can be seen clearly from earth surface will be a home to 80% of the population. These cities are built to adapt to constant change to the world, every road and architecture can be moved to a different place like in legos. These cities are built on flat surfaces, as mountains and any other obstacles are removed, if not kept for the purpose of decoration.
Buildings are now being built by robots with incredibly cheap cost and speed, even the poorest are living in big comfortable apartments with their own garden. There are about 7-15 of these cities, they are the main geopolitical forces on the globe, they are competing with one and other, yet achieved an amazing equilibrium of power and corporations. I call them MechaCities.