Llyn Ogwen is a located between two mountain ranges of Snowdonia, the Carnnedau and the Glyderau, in the north-west part of Wales. It is a natural and a very shallow lake with a depth of only 3 m (9.8 feet). It is fed by a couple of streams from the slopes of the mountains which enclose it, including Tryfan and Pen yr Ole Wen. The lake is the source of the Afon Ogwen, which is flowing north to reach the sea near Bangor. It has a dam which was built in the 20th century, in order to supply water for the use of the nearby Penrhyn Quarry.