It measures nearly fifteen metres across and rises only to about a metre in height, its surface oddly flat, with faint traces of a stony bank running around its outer edge. It is the kind of structure that could pass unnoticed underfoot, yet its regularity and definition mark it out as deliberate rather than accidental, a human arrangement rather than a geological quirk.

Knockmaa carries considerable weight in Irish mythology as the seat of Finvarra, the king of the Connacht fairies, and its summit holds more than one prehistoric monument. This smaller cairn, a term for a mound or heap of stones typically raised over a burial or as a territorial or ceremonial marker, is distinct from the larger cairn nearby and may represent a separate episode of activity on the hill entirely. Whether the two monuments were ever related in function or simply accumulated on the same prominent summit across different periods, the archaeology alone cannot say with certainty. What is clear is that the platform's circular form and perimeter banking follow conventions seen in prehistoric funerary and ceremonial construction across Ireland, suggesting it was laid out with some care and intention.