The rectangular structure at Carrowncashlane, measuring roughly 7.6 metres east to west and just under 7 metres north to south, has been reduced to its ground floor level, standing at a maximum height of 3 metres. What remains tells a story of medieval Irish architecture; the southern wall, 1.65 metres thick, still shows evidence of a window and built-in wall cupboards, whilst a doorway pierces the western wall, which measures 1.5 metres in thickness.

The castle’s history becomes somewhat murky when we delve into the records. According to the Civil Survey conducted between 1654 and 1656, Carrowncashlane formed part of the larger estate of Ballyknock, which in 1641 belonged to Darby O’Brien of Kilcomeragh. Curiously though, whilst O’Brien’s ownership is documented, no castle at Ballyknock appears in the official listings from that period, leaving us with an intriguing gap in the historical record.

Adjacent to the southwest corner of the castle lies a rectangular enclosure that archaeologists believe may have functioned as a bawn; a fortified courtyard typical of Irish tower houses and castles. These defensive enclosures were essential features of rural strongholds, providing a secure area for livestock and offering additional protection to the main structure during times of conflict. The relationship between this enclosure and the castle proper offers valuable insights into how these fortifications operated as complete defensive systems rather than standalone buildings.