Affentitten,
Land units cannot move into port hexes. If they are adjacent to a port hex, they can be transported out to sea. Look at Scapa Flow, Kiel, and Sevastapol and you'll notice a port without a city. They work, but Copenhagen, Bilbao, Lisbon, Tangier, Rome, Tripolitania, Beirut, and Istanbul (all cities without ports) do not.