+100% Harbor district adjacency bonuses.

If a civilization was going to have a naval and merchant fleet, it needed a lot of other things – docks, slips, wharves, warehouses, breakwaters, lighthouses, not to mention all those stevedores, shipwrights, harbor pilots, and others – to float ships and keep them afloat. Without this naval infrastructure, navies don’t last long. In the Middle Ages, for the first time, some kingdoms devoted substantial planning and funds to their naval facilities. For instance, the threat of Ottoman expansion brought the Venetian Republic to establish extensive shipyards (including the famous Arsenal), while the Fatimid Caliphate and Byzantine Empire needed efficient naval infrastructures to keep killing each other for two centuries.