This is a rath, the common Irish term for a ringfort, a type of enclosed farmstead built and occupied roughly between the sixth and twelfth centuries. Tens of thousands once existed across the island; this one at Gortnagrelly survives, just about, squeezed between modern infrastructure and the slow work of agricultural improvement.

The site takes the form of a raised circular area roughly twenty-five metres in diameter, enclosed by an earthen bank about two metres wide. A fosse, meaning a defensive ditch, runs around the outside of the bank, and a slight causeway crossing it at the north-north-west marks where the original entrance once stood. In most ringforts, this combination of bank and fosse would have defined a farmstead, offering a degree of enclosure for livestock and household alike rather than any serious military defence. At Gortnagrelly, time and practical need have eroded much of that original clarity. The fosse is now visible on the south-south-east to north-north-west arc only as a marginally wetter strip of ground at the base of the bank; on the north-north-west to south-east side, it has been re-cut and pressed into service as a field drain. The northern edge of the N16 runs directly along the outer line of the fosse on the south-east to south-south-west section, meaning the road has effectively consumed part of the monument's perimeter. A modern gap of two metres has also been cut through the bank on the southern side, presumably for agricultural access.

What remains is a quietly legible site if you know what to look for. The original entrance gap in the bank, four metres wide and still accompanied by a faint trace of its causeway, gives a sense of how deliberate and considered the layout once was. The wetter ground where the fosse survives undisturbed is worth noting too, a reminder that archaeology in Irish fields is often read through drainage patterns as much as through earthworks.