Amon Darthir was a mountain peak in the Ered Wethrin, south of Dor-lómin. The stream Nen Lalaith that flowed down into Dor-lómin near Húrin's house was fed from a spring that came down from this mountain. Beneath Amon Darthir's peak were a series of secret, difficult and narrow passes that were the only ways through the Ered Wethrin when coming from that direction.