The wide northern land of Hithlum was protected from east and south by a long curving mountain range known as Ered Wethrin. Near Amon Darthir, one of the most prominent peaks of the southern part of the range, a spur of mountains split away from the main line of Ered Wethrin and reached out into the plains of Hithlum for fifty miles or more. The shorter range was known as the Mountains of Mithrim, and it divided the southern part of Hithlum into two smaller regions. To the east was Mithrim with its great lake, after which the mountains were named, while to the west lay the land of Dor-lómin.