It is described in the Caernarvonshire Inventory, Vol. II, 170 (1144). Huts in Cwm Dwythwch. A small long hut and two sub-rectangular structures, on the mountain slopes W of Llyn Dwythwch, may be the remains of hafodau mentioned in 1352. (i) Ruined building, 25ft by 15ft 6ins, with walls 2ft 6ins thick of large stones set in clay. 1100ft above OD. Condition: poor. OAN site visit 2007. The ruinous foundations of a medieval longhouse forming part of complex that is shown on the current OS mapping. It is a rectangular structure with double thickness walls and measures 9m long by 5m wide. It is constructed of small/medium stones and boulders. The surviving foundations only stand to 0.5m with a hood wall on the west end. P.J. Schofield, OANorth, 8th June 2007