The roads of the Old World are all too often small, primitive and unprotected being commonly plagued by bandits and goblins. Therefore a considerable part of the traffic of cargo and people is handled by boats sailing upon large rivers, who connect cities and markets. The river boats pay tools to the local authorities and a part of the tolls is expended in the maintenance of river locks.
Rivers often double as political borders, being relatively easy to defend. An invading army is forced to use bridges and/or fords when an river is too wide to cross on foot. The control of such strategic chocking points is a high priority of any approaching army. Due such reasons all large rivers possess tremendous military importance.