This is a ring-cairn, a roughly circular enclosure roughly eighteen metres across, defined by a low earthen bank with a slight, enigmatic rise at its centre. That central mound, barely a few centimetres proud of the interior, hints at something older beneath: a monument possibly in the barrow tradition, the term used for a family of prehistoric burial mounds found across Ireland and Britain. The kerbing, a continuous line of low stones set against the outer face of the bank, is what makes Coolraheen genuinely unusual. Such kerbing is a marker typically associated with Bronze Age or Iron Age funerary and ritual practice, and here it survives in some stretches with quiet precision.

The best-preserved kerbing runs along the north and west quadrants, where two contiguous rows of stone meet near the northwest. In the northern stretch alone, ten stones survive across a length of 4.4 metres, ranging in height from ten to thirty-six centimetres. The western row runs a comparable 4.3 metres. Between them, additional stones fill the angle, though some have been displaced by the roots of a tree that has taken hold in the bank at the northwest, a slow botanical intrusion into what may be a structure several thousand years old. The overall shape of the enclosure, measuring 18.7 metres north to south and 17.7 metres east to west, is approximately but not perfectly circular, which is itself common in monuments of this period, built by eye and hand rather than instrument.

The hill setting is part of the monument's logic. From the northern edge, the ground opens out over the Dinin river valley, with mountains visible to the west and hillslopes to the east. It is the kind of elevated, outward-facing position that prehistoric communities across Ireland repeatedly chose for their ceremonial and funerary places, positioning the dead, or the rituals conducted on their behalf, at a threshold between settled land and open sky.