On the north-eastern bank of the Hell River, a watercourse that runs roughly north-west to south-east through the townland of Toonagh, a subrectangular cairn rises from the surrounding ground to a height of between 1.6 and 2.2 metres. Its base measures roughly 21 metres north to south and 12 metres east to west, and its top is notably flat, a platform of around 5 by 4 metres. Facing stones survive at the northern and southern ends, and on the western side a built earthen ramp climbs from the south to reach the summit, its outer edge retained by low walling. The whole structure is heavily overgrown, which gives it a quality of slow disappearance, something that was once deliberately shaped now quietly returning to the landscape.

The cairn sits just 9 metres west of what is recorded as an inauguration mound, a type of earthwork associated with the formal installation of Gaelic lords in early medieval Ireland. Such mounds were ceremonial focal points, places where a king or chieftain would be publicly recognised before his people, sometimes involving symbolic rituals of sovereignty. The proximity of this cairn to that mound is unlikely to be coincidental. The ramp, the flat top, and the carefully placed facing stones suggest this was not a simple burial cairn but something constructed to be used, perhaps as a viewing platform, a processional element, or some kind of ancillary structure within a wider ceremonial complex arranged along the river bank. The Hell River itself, with its striking name, adds a layer of local character to the site, though the origins of that place-name remain unexplained in what survives about the area.