In the Civ game, it's 'way too easy to build super harbors in places at which it shouldn't be possible. There are only a relatively few locations which would make great harbors...most costal areas have no natural inlets and bays (like New York Harbor, or Sydney, for instance). In this game, it's no problem building an equivalent to New York harbor in a place with no inlets at all (like the bland coast of west Africa).
I suggest that there be special coastal squares (at the mouths of rivers, and also on convoluted coasts) which would make great harbors, and that ONLY at these places can civs build the sort of harbors which can build modern warships. At any other places, it should be very difficult to build a great harbor. Now, civs will have to search for great harbor locations, just as they have to search for resources.
Also, there should be a small limit, except at the Great Harbor locations, to the number of ships that can be harbored at any location.
I suggest that there be special coastal squares (at the mouths of rivers, and also on convoluted coasts) which would make great harbors, and that ONLY at these places can civs build the sort of harbors which can build modern warships. At any other places, it should be very difficult to build a great harbor. Now, civs will have to search for great harbor locations, just as they have to search for resources.
Also, there should be a small limit, except at the Great Harbor locations, to the number of ships that can be harbored at any location.