Rectangular in shape, measuring roughly 3.8 metres along its longer axis and 2.7 metres across, and standing just 0.6 metres high, it is built directly onto a rock outcrop and composed largely of thin slabs and small stones. A cairn, broadly speaking, is a deliberate accumulation of stones, and the form has been used in Ireland across thousands of years for burial, commemoration, navigation, and boundary-marking. What makes this one unusual is the candid admission that follows its description: its antiquity is considered dubious. Whether it is genuinely ancient or something far more recent and mundane, nobody can say with confidence.

The cairn sits on the Iveragh Peninsula, one of the great fingers of land that reaches into the Atlantic from southwest Kerry, and a landscape with an extraordinary density of prehistoric and early medieval remains. Tomies mountain rises above the northern shore of Lough Leane, part of the Killarney valley. The specific site was catalogued by archaeologists A. O'Sullivan and J. Sheehan in their 1996 survey of the peninsula's archaeology, published by Cork University Press, which remains a foundational record of the region's field monuments. That survey applied the cautious label of dubious antiquity to structures whose origins could not be reliably established, distinguishing them from monuments with clearer prehistoric or early historic credentials. In other words, this cairn may be old, or it may simply be old-looking.