City Resource
From PotBS Wiki
Every port in the game has a certain number of City Resources associated with it. These city resources limit the kind of structures that may be built at the port. Most resources are used in the production of a certain commodity, with the exception of Public Docks, Natural Harbor, Deep Natural Harbor, and Regional Market. In addition, the Region Market does not have an associated structure, it signifies that there exists an Auction House in the port.
