Ports are buildings that can be constructed after you have researched the Sailing technology. Ports produce 2 population to the city it is built in. They cost 10 stars and can only be built on water tiles that are in your territory. Ports will also convert units that move onto it into boats.
Sea Routes Edit
When you have 2 ports or more, a sea route will form as long as they are close enough, and there are no direct land obstructions. Sea routes will connect cities and give +1 population to the connected city and the capital, functioning like roads. Before the "Power" update, sea routes did not have a tile limit. The max distance away from each port that still allows for a sea route has not yet been found.