Trawsfynydd Nuclear Power Station was constructed between 1959 and 1963 to architectural specifications by Sir Basil Spence. It started service in 1965 and its twin Magnox reactors generated electricity for 26 years before it reached the end of its service life in 1991; the station was closed in 1993. The first inland civil nuclear power station in the UK, it used fresh water for cooling drawn from Trawsfynydd lake, originally created in the 1920s as part of a hydro-electric project at Maentwrog.

The complex comprised accommodation grouped in four buildings, each of which fulfilled one of the station's distinct functions - reactor buildings, a turbine hall, fuel disposal areas and an electricity substation. These were arranged compactly and linked by covered walkways. The reactor buildings, which housed the station's twin Magnox reactors, were constructed of reinforced concrete and, at 180 feet in height, were the most dominant feature of the site. The Central Electricity Generating Board was keen to recognise that Trawsfynydd was a Welsh power station and so the practice produced a vast 'mosaic' in boulder-sized pebbles in the form of a Welsh dragon which formed the paving of the central court.

The power station is set within extensive landscaped grounds (NPRN 301093) designed by Sylvia Crowe, who also commented on the setting of the building to complement its wider landscape within the Snowdonia National Park. Decommissioning of Trawsfynydd began in 1993 and it is expected that site clearance will be carried out over the next 100 years. The concrete reactor buildings, which remain on the site, will be clad and become safestore buildings.
Sources include Magnox Electric plc Report, 1997.
RCAHMW, October 2009

Situated on the edge of Trawsfynydd Lake, within the Snowdonia National Park, Trawsfynydd is the only inland nuclear power station in the United Kingdom. Construction of the twin magnox reactor power station started on 1 July 1959. It began operating in March 1965, and was decommissioned in 2009. The lake itself was originally created in the 1920s to supply water for the Maentwrog hydro-electric power station (nprn 33605).

L. Moore, RCAHMW, 16 March 2011