Late Medieval Naval Arsenal

Venice's famous Arsenal — an entire walled city of slipways, ropewalks, and warehouses that could stack out war galleys at assembly-line pace — is the model for this expansion: a great shipyard where heavy warships are built while the ordinary shipyard next door keeps stacking merchant and light combat hulls. In the game the Naval Arsenal carries the heavy-warship line forward and remains the only place that class ever launches from.