The larger of the pair is crudely built and circular, measuring roughly 5.8 metres by 5.5 metres, with walls that survive to about half a metre in height and seventy centimetres thick. What makes it quietly odd is what lies within: a paved turf-platform, a feature that suggests the enclosure was not simply a field boundary or animal pen, but a small deliberate structure with some functional or perhaps ritual purpose, though the record does not commit to either.

The site lies on the Iveragh Peninsula, the broad finger of land in south Kerry that contains some of the densest concentrations of early field monuments in Ireland. Circular enclosures of this kind are common enough across the Irish landscape, often associated with early medieval settlement or agricultural activity, but the interior platform at Derrylahan gives this example a detail that sets it apart from the ordinary. A second, incomplete enclosure, slightly smaller at around 4.7 metres in diameter, lies nearby to the east, its outline fragmentary and unresolved. Whether the two structures were contemporary, or whether one preceded the other, is not known. Both were documented as part of an archaeological survey of south Kerry published by Cork University Press in 1996, compiled by Aidan O'Sullivan and Jerry Sheehan, a project that systematically recorded the remarkable density of ancient remains across this part of Munster.