Canvas Print of Pen y Garreg Dam from below, in the Elan Valley in Mid Wales. The Elan Valley is now in the county of Powys whereas previously it was a part of Radnorshire. The dams generally only overflow after spells of heavy rain. All the Elan Valley dams are accessible by car and some can be crossed on foot. Pen y Garreg is often regarded as the ‘middle dam’. The viaduct at Garreg Ddu lies further downstream.