This ringfort, known locally as a rath, measures approximately 16.35 metres across from north to south and 14.45 metres from east to west. The grassed-over stone wall that defines its perimeter still shows its original facings in places, particularly on the western side where the structure appears to have been about 1.8 metres thick. While time has taken its toll on much of the fortification, a modern wall now follows the old foundation along the entire eastern half, preserving the site’s circular footprint.

Just southeast of the centre stands an intriguing triangular outcrop of rock, measuring roughly 0.95 metres on each side and rising 0.42 metres high. Someone in antiquity took the time to carve a small depression into this stone; a modest hollow measuring 20 by 17 centimetres and 8 centimetres deep. Whether this served a ritual purpose, held offerings, or had some practical use remains a mystery, though such carved stones are often associated with ceremonial activities at Irish ringforts.

Ringforts like An Caiseal were once common across the Irish landscape, serving as defended homesteads for farming families during the early medieval period, roughly from the 5th to the 12th centuries. These circular enclosures, with their substantial stone or earthen walls, provided security for both people and livestock whilst also displaying the status of their inhabitants. The Glencolumbkille example, with its commanding position on elevated ground and substantial stone construction, would have been home to a relatively prosperous family who could afford such defences and who likely controlled the surrounding agricultural land.