It reads, at first glance, as little more than a grassy irregularity in the ground, but its dimensions tell a different story. The cairn, a burial or commemorative mound constructed from piled loose stone, stretches roughly 18.7 metres on its north-north-west to south-south-east axis and nearly 19 metres across, yet rises only half a metre from the surrounding ground. That combination of spread and flatness suggests considerable age, and the surface is pitted with hollows where stone has been lifted away over the centuries, a process archaeologists call robbing, in which building material was taken from older structures for use elsewhere.

The robbing has clearly been substantial enough to blur whatever original form the cairn once held. Its shape is described as irregular, which may partly reflect that interference rather than original design. On the north-north-west side, a later rectangular structure measuring four metres by three metres is still visible, defined by loose limestone blocks. The relationship between this smaller feature and the cairn itself is not entirely clear, though the word "later" implies it was added after the cairn's primary construction, perhaps by people who found the existing mound a convenient anchor or boundary for their own purposes. Inis Mór, the largest of the Aran Islands, is dense with layered occupation, and it would be unremarkable for a prehistoric monument to have attracted subsequent, unrelated use.