The structure is a cashel, a type of ringfort defined by its stone construction rather than earthen banks, and this one is modest in scale, measuring roughly nineteen metres northeast to southwest and just over twelve metres in the perpendicular direction. What makes it quietly arresting is not its age as a settlement site but what it became long after anyone last lived within its walls: a cillín, a children's burial ground.

Cilliní were informal, unconsecrated burial places used across Ireland for centuries, most often for unbaptised infants who, under Catholic doctrine, could not be interred in consecrated ground. The chosen sites were frequently liminal, already-ancient places set apart from the ordinary landscape, and the old cashel at Foghill fits that pattern exactly. The enclosing stony bank, up to 2.8 metres wide and best preserved along its southern half, still stands to an external height of 1.4 metres on the northeast side, where the builders compensated for the natural slope by building up the outer scarp. The interior surface is uneven and stony, sloping slightly downward toward the northwest, and low upright stones protruding from the ground are likely grave markers. No clearly defined entrance survives, only a low gap of about two metres in the bank to the northeast.

The site today has the look of something half-returned to the land. Field clearance stones and boulders have been heaped against the bank, particularly along the northern arc, and the interior is colonised by thistles and brambles. Below the slope, flat damp pasture gives way to sand dunes to the northeast, with Lacken Bay beyond. The bay frames the whole quietly, lending the enclosure a coastal exposure that feels at odds with the stillness inside it.