patrick.net

@Dan8267 I was hoping they'd talk about how Cairo and Amsterdam both developed into major trading centers partly because of the free north-south transportation along a river to a sea. Nile/Rhein to Mediterranean/North Sea.

Free transport because in both cases, the wind blows from north to south, and the river flows the other way. So you can put up the sails to go south and take them down to go north.