Pen y Garreg dam, Elan Valley, Rhayader

It’s all downhill from here. Pen y Garreg

This copper-domed valve tower sits on top of the Pen y Garreg dam, one of six dams in Mid Wales's picturesque Elan Valley which help supply water to England’s second-largest city. On the other side of the tower, water thunders over a 123ft (37m) drop, part of an elaborate system of dams, reservoirs and a 73-mile aqueduct built in the late 19th century to channel drinking water to Birmingham. Work on this huge feat of civil engineering began in 1883 and the first four dams, including Pen y Garreg, were completed by 1904. Elan Valley sits in the Cambrian Mountains so water flows downhill from the high valleys to Birmingham without needing to be pumped. It travels at less than two miles an hour, taking up to two days to reach the city’s Frankley reservoir.

That little tower you can see in our homepage picture can be accessed by a tunnel, lit by openings in the dam wall, which, after wet weather, are concealed behind a roaring curtain of water. The dams and reservoirs are a major visitor attraction in this area. It’s also home to 12 sites of special scientific interest, plenty of wildlife, walkers, mountain bikers and, thanks to low levels of light pollution, has International Dark Sky Park status.