It measures roughly sixteen metres along its longer axis and six metres across, and it sits within the north-eastern corner of a larger hilltop enclosure. To a passing eye it could be a natural undulation in the ground. It is, in fact, a children's burial ground.

Places like this are scattered across Ireland, and they carry a particular weight of history. Known in Irish as cillíní (the singular is cillín), these were informal burial grounds used for unbaptised infants and others considered ineligible for consecrated ground under Catholic Church practice, a custom that persisted for centuries and in some areas well into the twentieth century. The children buried in them were not forgotten by their families, but they were excluded from the formal rituals of Christian burial, and so their resting places tend to be quiet, unmarked, and set apart, often on boundaries, hilltops, or ancient earthworks. The Cloonagh site follows that pattern closely: it occupies the north-eastern quadrant of a pre-existing hilltop enclosure, a feature that in the Irish landscape usually indicates much older, sometimes prehistoric, use of the ground. The pairing is not accidental. Marginal and liminal spaces, places already set apart from the ordinary world, were chosen with some regularity for cillín burials.

What survives at Cloonagh is the mound itself, subrectangular in shape and low enough to be easily overlooked. No grave-markers are visible at the surface.