When trying to build a new city you must first obtain a flat.then send 250 workers and 10,000 of each resource and 10.000 gold to that flat. in addition, you will also have to have 250 workers and 10,000 of each resource and 10.000 gold in your current city also you are required to have the correct title to be able to build another city.once there you can click the build city button and after some time your new city will be erected! This information is in-game as well, hover over the little fort icon at bottom right of your interface.
