This is a cashel, the term used for a ringfort built from stone rather than earthen banks, and the example at Derrylehan is modest enough that a casual walker might take the collapsed boundary for a natural accumulation of field clearance rather than something deliberately constructed.

The enclosure measures around 33 metres in diameter, with the remains of its wall surviving to a thickness of roughly three metres and a height of just one metre at its tallest. Unlike many similar sites, there is no fosse, the defensive ditch that typically rings an earthen ringfort, which is consistent with a stone-built construction where the wall itself provided the primary enclosure. Two breaks in the wall, one on the west side at about three metres wide and another on the east at just under three metres, may indicate where the original entrance once stood, though after centuries of collapse it is impossible to say with certainty which, if either, is the genuine threshold. The slight south-westerly slope and sheltered hollow in which it sits suggest a practical choice of location, offering some natural protection from prevailing weather while keeping the site on workable ground.