It looks, to a careful eye, as though it should not be there, at least not in that form. The roughly oval stone cairn measures around 13 metres from north-east to south-west and 17 metres from north-west to south-east. Its northern edge drops steeply into the lake; the other sides slope away more gradually. Nothing about the landscape quite explains it.

A crannog is an artificial island, typically built up from timber, stone, and organic material, and used as a defensive or domestic dwelling place, most commonly from the early medieval period onwards in Ireland. When this site was inspected in 1988, none of the material evidence that usually confirms such an origin, such as preserved timbers or animal bones, was found. Even so, the mound's clearly artificial appearance, combined with its close proximity to two other confirmed crannogs lying roughly 100 metres and 170 metres to the east along the same lough shore, made a convincing circumstantial case. The cluster of three such structures in the north-west corner of Ballymore Lough is quietly unusual; crannogs tend to be solitary features, and finding several in loose formation on a single lake raises questions about the community or communities that built and used them, questions the current evidence does not yet answer.