What appears at first glance to be a modest field boundary is in fact a cashel, the Irish term for a ringfort built from stone rather than earthen banks. Thousands of these circular enclosures survive across Ireland, most dating from the early medieval period, and they served variously as farmsteads, livestock enclosures, and defended homesteads. This one at Derrygarriv is sixteen metres in diameter, defined by the low grass-covered base course of a drystone wall, now worn down to roughly twenty centimetres in height and a metre thick.

What makes this site quietly layered is the evidence of later activity built directly onto the original structure. A second drystone wall, considerably taller at 1.2 metres and thinner at 0.4 metres, was added along the outer rim of the original cashel at some point after its construction, suggesting the enclosure was reused or adapted in a later period, though for what purpose is not recorded. Field boundaries have grown up against the cashel at the north-west and south-east, incorporating it gradually into the working landscape around it, and field-clearance rubble has been piled intermittently against the outer face of the wall. That rubble is telling: generations of farmers removing stones from surrounding land found the old wall a convenient place to dump them, which is part of why the original structure is now so difficult to read at ground level. The site sits on a level terrace, which would have made it a practical and defensible location for an early medieval settlement looking out across the north-facing slopes below.