Penygarreg Dam & Valve Tower

Penygarreg Dam and Valve Tower is a masonry dam constructed with large, heavily rock-faced blocks. It features spillways at both ends, which have parapet walls and broaden as they descend, surfaced with hard stone. The walls of the spillways turn to become parallel to the stream and include arched outlets. Near the top of the downstream side, there is a series of square windows, and below these, two rows of protruding blocks that were used to support scaffolding during construction. At the bottom of the dam, there is a massive circular outlet framed by an aedicule-like surround with piers at each end and a pediment above.

At each end of the dam, there are platforms with steps leading down to the top of the dam. In the center of the dam, there is an attached round valve tower topped with a copper dome, which features a lantern and a fish weathervane. The tower has waterspouts around its circumference, with square windows in the upper section and round arches with two-light windows below. On the downstream side, there is a doorway leading onto a raised platform that rises from the top of the dam, with steps leading to the top of the dam. The valve tower is corbelled out over a narrower polygonal stage that has barred intake windows and extends below the water level. The interior is said to contain the original operating machinery.