It measures roughly seven metres across, defined by a fosse, which is a shallow ditch, and a low external bank encircling the inner area. To the naked eye on the ground, it may register as little more than a slight unevenness in the soil. It was aerial photography that brought it properly into focus.

This kind of monument is known as a ring barrow, a burial form widely used in prehistoric Ireland, typically consisting of a central mound or platform enclosed by a ditch and an outer earthen bank. They are associated broadly with the Bronze Age, though examples span a considerable chronological range. What is notable about the Dundonnell example is less its scale, which is modest, and more the conditions it occupies. Poorly drained, low-lying ground is not the terrain one usually associates with these monuments, which more commonly appear on elevated or well-drained positions where they command or are visible across a wider area. Whether that reflects something particular about how this site was chosen, or simply the degree to which surrounding land use has altered the character of the ground over millennia, is difficult to say. The circular form itself was identified through satellite imagery rather than fieldwork or excavation, meaning almost everything beneath the surface remains unknown.