Poros

This was a large river and the largest eastern tributary of the Anduin river, it arose high in the vales of the southern Ephel Dûath and descended in a wide valley to join the Great River about forty miles north of the Anduin’s Delta, it formed a natural barrier between South Ithilien and the Harad lands, and thus was often a frontier of war. The river was very wide and thus could only be forded safely at one point, the Crossings of Poros.