Cities can be built via the "My Nation" dropdown menu. On this page you may construct new cities, or manage current ones. Under current cities the total population for each city is shown, as well as the city type. By clicking on the Manage button, you are directed to a page with statistics, infrastructure and services for your city. If you click on City Options, you can rename, upgrade or demolish your cities.
There are currently 4 types of cities.
Building a town causes your population to grow by 10 000. Upgrading a town to a city causes your population to grow by 40 000 and upgrading a city to a metropolis causes your population to grow by 100 000