It is a cillín, an unofficial burial ground of the sort once used across rural Ireland for unbaptised infants and others who, under Catholic ecclesiastical law, could not be interred in consecrated soil. The stones that mark it are small, grassed over, and easy to miss entirely.

The plot sits just north of centre within the ringfort, measuring roughly 14 metres north to south and 4.6 metres east to west, unenclosed and open to the surrounding earthwork. Ringforts, the circular enclosures that dot the Irish countryside and date broadly from the early medieval period, were often regarded in folk tradition as liminal or otherworldly spaces, associated with the fairies and therefore outside ordinary social order. That liminality made them a recurrent choice for cillín burials, which were themselves a practice rooted in sorrow and pragmatism, a way of placing a child somewhere apart, yet not entirely abandoned. The visible stones at Castlegrove are set rather than scattered, suggesting the burials were marked with some intention, even if the markers were never meant to be monumental.

The site gives little away on approach. The grassed-over stones are the only outward sign of what the ground contains, and they require a close and unhurried eye to read properly.