Celduin

The Celduin (or Running) is a river of Rhovanion. The Celduin is a 600–Númenórean miles long river that runs from the Lonely Mountain south through the Long Lake, where it is joined by the Forest River, and thence through the eastern outskirts of Mirkwood, then south east through apparently uninhabited regions of Rhovanion to its confluence with the Carnen and finally in a long south-eastward loop to the great inland Sea of Rhûn, past the land of Dorwinion.