The north gable of a three-storey limestone rubble house still stands to something approaching its full height, with a chimney projecting outward near its centre, a collapsed pair of windows flanking the chimney breast at second-floor level, and a small fireplace with a rectangular wall-cupboard beside it surviving internally at first-floor level. The whole thing is heavily clad in ivy, inside and out. The east side of the building, which would have told us considerably more, collapsed in 1954 and the rubble was cleared away. A small archway once adjoined the east side of the gable, and the ground around the house was at some point cobbled, though neither feature is visible today.

The site sits on a low hill with open views to the north and west, and what survives on the surface represents only part of what was once here. The Down Survey, a systematic mapping of Ireland carried out between 1655 and 1656 under the direction of William Petty, recorded land ownership and settlement across the island in considerable detail following the Cromwellian conquest. Its barony map of Kells, County Kilkenny, shows 'Rathculbyne' with two distinct structures: a substantial castle and, beside it, a gabled house with a chimney at one end. That second building is almost certainly the ruin visible today. The first, the castle proper, has left no visible trace above ground, though the map evidence strongly suggests it once stood here. The 1839 Ordnance Survey six-inch map already describes the site as a ruin, as does the 1948 revision, so the decay had advanced well before the eastern collapse of the mid-twentieth century. The 25-inch Ordnance Survey map, produced between those two dates, picks out the north gable specifically, which gives a sense of how prominent even this single surviving fragment appeared in the landscape.