Plas Tan-yr-Ogof including adjoining walls and arches to E and W

Plas Tan-yr-Ogof is a rectangular, two-storey house built in the 18th century, constructed from local limestone rubble with limestone dressings and featuring cast-iron Gothic windows. The roof is flat with crenellated and corbelled battlements. A set-back, storeyed, and battlemented porch projects from the front, containing the main entrance, which is accessed by three concrete steps leading to a deeply-chamfered Tudor-arched opening with a modern door. To the left, on the return of the main east wall, is a large Tudor-arched window with six lights and Perpendicular tracery in cast iron. The main (road-facing) facade has two-light Tudor windows on both floors, with cusped heads, diagonal iron glazing bars, and flat, returned labels. A single-light window appears centrally; this was originally a segmentally-headed entrance. Above it, a projecting sandstone shield is positioned between two Tudor windows, although the heraldry or inscription is no longer visible. A large, modern entrance with double doors has been added to the left. The rear of the house features six pointed-arched entrances, each with a corresponding fine, pointed-arched tracery window above. A modern external fire escape has been added to the far-right entrance, and a modern window insertion is located above the second from the left. The battlemented parapet extends along the rear, but without corbelling. A further arched window is present on the west side, featuring deeply-recessed intersecting tracery and small-pane glazing. Adjacent to this is a ruinous, mono-pitch lean-to with semi-ruinous rubble walls, approximately 1 meter high, adjoining the north side. To the east and parallel with the road, a short section of rubble wall steps up at a Tudor-arched entrance. This is followed by a further 60 meters of crenellated wall, standing approximately 1.5 meters high and with widely-spaced crenellations, which terminates at its junction with a lower rubble wall featuring 'cock and hen' coping. A section of corbelled and crenellated wall, 3 meters high, runs along the roadside, adjoining the porch to the west. It steps up above a wide Tudor-arched entrance, and continues to adjoin Tan-yr-Ogof Farmhouse. The interior of the house was not inspected during the survey.