Ports are buildings unlocked with the Sailing technology. They cost 10 stars, can only be built on shallow water tiles, and provide 2 population. Ports are considered one of the most integral buildings since they allow for naval access.
Connecting a city to the capital gives one population to the connected city and the capital. Ports must be adjacent to a city or connected to a city by Roads to be used to form a city connection. Ports can form city connections with other Ports that have three or fewer water tiles between them.