The Claerwen dam is the highest of the Elan Valley dams. Outflow water runs along the valley to feed the Caban Coch reservoir, further down. The dam took six years to complete and is twice the size of any other of the dams in the Elan Valley. Although it was completed in 1952, it was designed in a Victorian style to blend in with the other dams in the valley. The expanse of upland between Rhayader and Pontrhydfendigaid is a designated National Nature Reserve. This viewpoint is looking down from the top of the dam.