The Vyrnwy dam is 45 metres (146 ft) high from the bottom of the valley, and 37 metres (120 ft) thick at the base; it is 355 metres (1,165 ft) long and has a road bridge running along the top.
It is decorated with over 25 arches and two small towers each with four corner turrets rising 4.3 metres (14 ft) above the road surface.

The dam was the first to carry water over its crest instead of in a channel at the side.
At the bottom of the dam is a body of water known as a stilling basin  necessary to absorb the energy when the water flows over the crest and into the valley, and to stop the water eroding the foundations of the dam.

A power house located under the west tower contains an electrical generator driven by water leaving the reservoir.
Before mains electricity arrived in the 1960s this was the area's only source of power.

About 1,200 metres (0.75 mi) from the dam is the reservoir's straining tower.
Standing only 30 metres (98 ft) from the shore, its purpose is to filter or strain out material in the water with a fine metal mesh, before the water flows along the aqueduct to Liverpool.
Its architecture represents Gothic revival, built at the same time as the dam.
The tower as a whole is 47 metres (154 ft) tall, 32 metres (104 ft) of which is above top water level, and is topped with a pointed copper-clad roof, coloured light green.

The west and east towers release compensation water by huge valves, which flows into for the River Vyrnwy, which would otherwise dry out unless in flood.
Depending on the water levels downstream the reservoir can release anything from 25 to 45 megalitres (5,500,000 to 9,900,000 imp gal) of compensation water per day.
The flow is measured by Natural Resources Wales at a weir a few hundred metres downstream.
The Vyrnwy dam is 45 metres (146 ft) high from the bottom of the valley, and 37 metres (120 ft) thick at the base; it is 355 metres (1,165 ft) long and has a road bridge running along the top. It is decorated with over 25 arches and two small towers each with four corner turrets rising 4.3 metres (14 ft) above the road surface.
The dam was the first to carry water over its crest instead of in a channel at the side. At the bottom of the dam is a body of water known as a stilling basin  necessary to absorb the energy when the water flows over the crest and into the valley, and to stop the water eroding the foundations of the dam.
A power house located under the west tower contains an electrical generator driven by water leaving the reservoir. Before mains electricity arrived in the 1960s this was the area's only source of power.
About 1,200 metres (0.75 mi) from the dam is the reservoir's straining tower. Standing only 30 metres (98 ft) from the shore, its purpose is to filter or strain out material in the water with a fine metal mesh, before the water flows along the aqueduct to Liverpool. Its architecture represents Gothic revival, built at the same time as the dam. The tower as a whole is 47 metres (154 ft) tall, 32 metres (104 ft) of which is above top water level, and is topped with a pointed copper-clad roof, coloured light green.
The west and east towers release compensation water by huge valves, which flows into for the River Vyrnwy, which would otherwise dry out unless in flood. Depending on the water levels downstream the reservoir can release anything from 25 to 45 megalitres (5,500,000 to 9,900,000 imp gal) of compensation water per day. The flow is measured by Natural Resources Wales at a weir a few hundred metres downstream.
Lake Vyrnwy