At roughly 25 metres across and over four metres high on its eastern side, it is a substantial presence on the ridgeline, and on the east face the mound abuts a natural rock outcrop nearly five and a half metres tall. That outcrop, with its suggestion of a sealed or blocked opening, caught the imagination of local tradition, which identified it as Fionn Mac Cumhaill's table, a detail recorded by the antiquarian Borlase in 1897.

The cairn, a prehistoric burial monument of the type built from heaped stones rather than shaped masonry, appears in the Civil Survey of 1654 to 1656, where it is described as "a great heap of Earth and stones called Shyfyne uppon the topp of the Mountaine of Slievnamam". The name Shyfyne is intriguing, though its precise meaning is not firmly established. The structure sits in loose alignment with two passage tombs, a form of Neolithic monument in which a stone-lined corridor leads to a burial chamber, located across the county boundary in Kilkenny: Knockroe lies approximately 11 kilometres to the east, and Baunfree around 13.5 kilometres to the east-northeast, suggesting this part of the upland landscape held some significance across a wide area in prehistory.

Hill-walkers have, over time, added to the summit of the cairn, compacting it into a tidier shape than it would originally have presented. That layer of modern addition sits quietly on top of something far older, and the views from the cairn extend in nearly every direction, broken only slightly to the west by the shoulder of the summit itself.