Geograph - photograph every grid square

The base of the unfinished dam at Dol-y-Mynach the lowest of the three dams planned for the Claerwen Valley was Dol-y-Mynach.
The work on this dam had to start at the same time as the other dams in the next valley, so that there would be enough of the dam above water to continue with the building later on.
But the dam at Dol-y-Mynach, which was to have been almost 31 metres (101 feet) high and 286 metres (938 feet) long was never finished, and the other two dams above it were not even started. A much bigger dam higher up in the valley, the Claerwen Dam, was completed in 1952.
When water levels are low enough you can see the base of the dam that wasn't finished, and it shows how the Victorians built the other dams. There are huge stone blocks of around ten tons each in the middle, set in solid concrete, with well-cut masonry on the outside.