The Glogn (Romansh, German: Glenner) is a whitewater river in Graubünden.
The river rises near the border with Ticino and is surrounded by up to 3100m high mountains.
In the upper reaches of the river has cut a deep gorge, which has uncovered black shale in a few places.
During the snow melt and after rains the river water is usually dark gray.
You can help Wikipedia by expanding it.This article related to a river in Switzerland is a stub.