The site is officially recorded as a children's burial ground, a type of place known in Irish as a cillín, where unbaptised infants were interred outside the bounds of consecrated parish cemeteries. Catholic doctrine, as it operated in rural Ireland for centuries, held that unbaptised children could not be buried in hallowed ground, so families quietly laid them in liminal places, often old earthworks, field margins, or coastal strands, that existed at the edge of the official world. A rath, which is a roughly circular enclosure defined by earthen banks and ditches and typically dating to the early medieval period, would have felt like appropriate ground: old, set apart, already carrying a certain weight of otherness.

The earthwork at Lissaleen sits on a south-facing slope in grassland, and it is a substantial one. Nearly circular in plan, it measures 47 metres north to south and 46.5 metres east to west, and is defined by three banks with two intervening fosses, the term for the ditches between them. The inner bank remains visible along the western, northern, and eastern sides, while elsewhere the enclosure is defined by a scarp, a natural or cut slope rather than a built-up bank. The middle bank survives across the southern, western, and northern arc, and the outermost fosse and bank can still be traced, though only faintly, at the south-south-west. The interior has been disturbed by tillage ridges running north to south, and several field banks and a road pass close by the monument. Despite all of this activity across the centuries, the site is described as being in fair condition, meaning its essential form remains legible in the landscape.