Alwen Dam

Alwen Dam is a 20th-century structure built from in-situ reinforced concrete and rock-faced concrete blockwork. It features a distinctive curved shape, measuring approximately 157 meters in length, with a battered face that sweeps out at the base. A spillway located on the southwest face discharges into a rectangular basin, which includes an iron weir at its outfall.

At the top of the dam, there are 12 arches supported by rusticated concrete piers that rise from the dam face. These arches carry a reinforced concrete footway and extend upward to form piers for a pipe handrail with cast iron stanchions. After the eighth open arch from the southwest, the design transitions to a tall open-arched tower in an Italianate style. The voussoired arches of the tower are set back beneath the corner piers, which ascend to a wide cornice featuring three bold guttae in the rusticated recess between the end piers. Both the outer and inner faces of the tower's arches have balconies made of reinforced concrete.

At the base of the dam, directly below the tower, is the turbine house. This structure has a recessed rusticated front beneath a moulded arch that spans between the battered end piers, all topped with a shouldered gable. The turbine house features a central pair of timber doors and is covered with sheet plastic roofing.