It is, in fact, the remains of a rath, a type of ringfort constructed during the early medieval period in Ireland, typically between roughly 500 and 1000 AD. These enclosures, built from earthen banks rather than stone, served as enclosed farmsteads for individual family units, and thousands of them survive across the Irish countryside in varying states of preservation.

This particular example at Sunfort measures approximately 38.6 metres north to south and 37 metres east to west, forming a near-perfect circle. The enclosing bank, or rampart, survives as a low, wide rise: standing roughly 0.85 metres above the interior ground level and about 0.55 metres above the exterior. Those are modest dimensions, suggesting either gradual erosion over more than a millennium or a structure that was never especially monumental to begin with. Along the northern side, a faint trace of an external fosse remains visible. A fosse is simply a ditch, dug to provide material for the bank and to add a further obstacle around the perimeter. That it survives only faintly to the north, and seemingly not elsewhere, hints at centuries of agricultural activity slowly softening what was once a more defined feature.