The Falls of Sirion were the mighty thundering falls of the River Sirion, just south of the Aelin-uial, where its waters fell beneath the earth and flowed under the hills of the Andram for nine leagues before emerging again at the Gates of Sirion. The Sirion's source was at Eithel Sirion on the eastern side of the Ered Wethrin, which lay in between Ard-galen (later Anfauglith) and Mithrim and Hithlum. It was guarded by the tower of Barad Eithel.