The growth is not random; it traces the line of a fosse, the shallow encircling ditch that defines a ditch barrow, a low prehistoric funerary or commemorative mound type where the boundary rather than any raised central feature is the primary surviving element. Here the fosse is modest even by those standards: roughly one and a half metres wide and just ten centimetres deep, enclosing a circular interior about five metres across. The interior itself is level and clear of overgrowth, which makes the reed-lined ring around it all the more legible once you know what you are looking at.

The site was not found by anyone walking the land with a purpose. It came to light through aerial photography, specifically through the Bruff Survey, which captured it on photograph reference 2090. Aerial survey has been one of the principal means of locating low-earthwork sites across Ireland, since the differential growth of vegetation over buried or semi-buried features can show up clearly from above even when the ground tells you almost nothing. A second barrow sits roughly ten metres to the north-east, suggesting this corner of Ballynagrana was used over some period for purposes that left only the gentlest of impressions on the landscape.