This is a rath, the Irish term for a ringfort, the kind of enclosed farmstead that was once the basic unit of rural life across early medieval Ireland. Thousands survive in various states across the country, but what makes this one at Ballyhiernaun worth pausing over is the detail of what the enclosure still holds, and what has quietly swallowed parts of it.

The bank that originally defined the site runs roughly south-southeast to northwest and measures just over 72 metres across its longest axis. It is primarily earthen, though some stones are worked into its fabric, and it presents a noticeably steep outer face, dropping about a metre on the external side, while the interior lip is much lower. At the northwest, the bank has been absorbed into a later field boundary running east to west, a common fate for these structures as farming arrangements changed around them over centuries. At the southwest there is a gap of roughly 2.8 metres, which now serves as the way in, though surveyors note this may not have been the original entrance. Inside, the ground levels off at the centre, and slightly east of that midpoint sits a low square platform, about 13.5 metres on each side and raised only 25 centimetres above the surrounding surface. At the northwest corner of this platform, there are traces of what may be a circular hut site, the kind of small, round domestic structure typical of early medieval occupation. Dense blackthorn has taken over the southern half of the interior and the northwest quadrant, ringing the perimeter and gradually engulfing a field fence that cuts across the site from north to south.