Maen Llia

Maen Llia is a standing stone which sits on moorland at grid reference SN924192 in the Brecon Beacons National Park in Powys, Wales.

The stone which is a large piece of intraformational conglomerate from the Old Red Sandstone measures 3.7 m high by 2.8 m wide by 0.9 m. It is roughly diamond-shaped and is partly moss-covered. It sits on a purpose made stone and earth mound.

The stone has seven sides, and is distinctly geometric in shape, although now much eroded. The centre line of the slab like stone is aligned precisely North/South, and its North pointing top edge has an elevation angle that matches the stones Latitude of 51.86 degrees. This makes it the correct shape and orientation to qualify as an horizontal sundial.