Llyn Mair

Llyn Mair (Welsh for 'Mary's lake') is a 14-acre (5.7 ha) artificial lake near Maentwrog, in Gwynedd. It lies in the area of Tan-y-Bwlch a little above Plas Tan-y-Bwlch, and is in the catchment area of the River Dwyryd. It was created by William Edward Oakeley (of Plas Tan-y-bwlch) as a 21st birthday present for his daughter Mair and as a water supply. It was built in 1889, and the nearby smaller Llyn Hafod-y-Llyn dates from the same period.

Plas Tan y Bwlch is thought to be the first house in North Wales with electric lighting powered from its own hydro-electric station, which was commissioned in the 1890s. A pipeline from the lake fed water to a Pelton wheel, which was located in a small power house on the hillside immediately behind the house. It ceased to operate soon after 1928, when the public hydro-electric power station at Maentwrog began supplying the area. In June 2013 a new hydro-scheme, costing £420,000, and similarly tapping the water from Llyn Mair, was opened. The water falls 60 m to the turbine, and the scheme is expected to meet most of the Plas' electricity needs.

The lake is set alongside the B4410 road, a minor road linking the hamlet of Rhyd. The position