A rectilinear stone spread measuring 4m east-west by 3.25m and 0.15m high. It was probably the remains of a building associated with the construction of the Grwyne Fawr reservoir in the early 20th century, although the lack of mortar or concrete in the rubble might suggest otherwise. Grass was growing over the stone when the feature was recorded in September 2007. J.J.Hall, Trysor, 27 September 2007