The Enchanted river.
The wells of Esgalduin was in Ered Gorgoroth. One of them ran as borderline between Dor-Dinen and Nan-Dungortheb and the other came 20 miles further West from the mountains into Nan-Dungortheb; ran South-East 20 miles til the junktion with the other. It crossed the land in an almost straight line South South-West for 40 miles to it reach the eaves of Neldoreth and the crossing Iant-Iaur and then disapeared into the forest behind the Girdle of Melian and the realm of Doriath. For another 45 Miles it ran straight South, halfway through with a big fall, until it made a great curve West and followed at the Northens side Neldoreth and on the Southern side Region 50 miles until it met Sirion. It was on the Eastern side of the curve Menegroth was delved.