What makes it quietly distinctive is what lies within: plain, uninscribed stone grave-markers, clustered particularly in the eastern half, with no names, no dates, and no inscriptions of any kind to identify who rests beneath them.

This is a cillíneach, a type of burial ground found across Ireland and used historically for the interment of unbaptised children. Catholic doctrine, until relatively recently, held that unbaptised infants could not be buried in consecrated ground, and so communities established their own informal, liminal spaces for the purpose, often at the edges of fields, beside ancient earthworks, or on marginal terrain like this gorse-covered slope. The word cillíneach derives from the Irish cill, meaning a small church or monastic cell, though many such sites have no ecclesiastical connection at all; the name speaks more to a sense of sacred separation than to any formal religious function. The Derreen site measures roughly eighteen metres east to west and ten metres north to south, enclosed on three sides by a wall that now survives only in fragmentary form, standing no more than thirty centimetres high in places. Local knowledge identifies it as a children's burial ground, and the plain markers bear that out: these were modest burials, carried out with care but without the formal apparatus of parish record or headstone inscription.

Cillíní of this kind were once widespread and are now often overlooked or mistaken for field boundaries or natural clearings. The unmarked stones at Derreen are easy to miss, but the site retains a particular quietness that sets it apart from the surrounding landscape.