It is oval in plan, roughly four metres long and two metres wide, and sinks no deeper than about 0.8 metres at its lowest point. To a casual eye it might be nothing more than a patch of waterlogged ground. What it likely represents, however, is the collapsed remnant of a souterrain, one of the stone-lined or rock-cut underground passages that were built across early medieval Ireland, typically for food storage or as places of refuge during times of danger.

The gap between what was once here and what survives is considerable. Writing in 1914, a researcher named Neary recorded a souterrain measuring thirty feet long, twelve feet wide, and four feet deep, a substantial underground chamber by any measure. That structure, which sat in the north-eastern quadrant of the ringfort, has since collapsed or been buried to the point where those dimensions are unrecognisable on the surface. The muddy hollow that remains runs roughly north to south, and is all that survives of what Neary described. The ringfort itself, a circular enclosure of the kind that was the standard rural settlement type in early medieval Ireland, provides the wider context: souterrains are frequently found within such enclosures, and the two features are generally understood to belong to the same period of occupation.