Port (STW building)
It doesnt produce units.
A Port provides a trade bonus to the income of a region. It also allows units to be moved directly to any other port owned by the Daimyo.
A port can be built in any coastal province that contains a castle. It allows the training of emissaries and spies, and also gives a trade revenue bonus. It also allows the transport of military units by sea to other provinces. A port is a necessary building before the Trading Post and Gun Factory improvements can be constructed at larger castles.