The cairn at Illane, overlooking the Coomhola river valley, rises only about a metre above the surrounding ground and stretches roughly seven metres across, most of its mass long since claimed by the encroaching bog. What gives it away are two upright stones still standing on its perimeter, one to the east and one to the west, each around 0.8 metres tall, their modest scale in keeping with the quiet, slightly submerged character of the whole structure.

What makes the site more than just an isolated mound is what lies a short distance to its west. Just 5.5 metres away stands a five-stone circle, a type of monument particular to the Cork and Kerry region, consisting of five stones arranged in a circle with one notably recumbent stone lying flat between two upright portal stones. The proximity of the cairn to such a monument is unlikely to be coincidental. These two features together suggest a ceremonial or funerary landscape, probably Bronze Age in origin, in which the ridge above the Coomhola valley held some sustained significance for the people who shaped it. The site was catalogued by Seán Ó Nualláin in 1984 as part of his systematic work on stone circles and related monuments in the southwest of Ireland.