It is not dramatic in scale, measuring roughly 1.8 metres north to south and standing just over a metre high, and yet something about its placement feels deliberate in a way that outlasts the centuries. A cairn, in the prehistoric Irish tradition, is typically a mound of stones raised over a burial or as a territorial or ritual marker, and this one commands the kind of elevated position that suggests it was never meant to be ignored.

The cairn occupies the summit of a northeast to southwest ridge, northeast of Three Castle Head, the promontory most associated with the thirteenth-century Mac Mahon castle complex below. The structure is roughly cone-shaped and built from medium-sized stones. What makes it particularly interesting is the evidence of its earlier form: traces of a kerb, the ring of upright or closely packed stones that would originally have defined the cairn's outer edge, protrude from the shallow peat along the southwest and northeast arcs. Kerbing of this kind often indicates a more substantial or formally constructed monument beneath the accumulated centuries of peat growth, suggesting the cairn may once have been larger and more clearly defined. At some point in recent times, visitors have rebuilt the upper portion, which means the top of what stands today is not quite what archaeology left behind.