It is a barrow, a prehistoric burial monument, though here the form is slightly unusual: rather than a raised mound, what you find is a circular hollow roughly 12.2 metres across, enclosed by a low bank of loose stone. That bank stands between 0.4 and 0.9 metres high and about 1.5 metres wide, giving the whole thing a sunken, bowl-like quality. There are deliberate gaps in the bank, one to the north measuring 1.3 metres and a narrower one to the south at 0.8 metres, suggesting these were original features rather than later damage. A section of drystone wall, the kind of rough unmortared construction found all across the Irish uplands, runs up the slope and meets the western side of the monument, though whether this wall is contemporary with the barrow or a much later addition is not recorded.

Barrows of this kind are broadly prehistoric in origin, serving as funerary monuments, though their precise dates vary enormously across Ireland. This particular example sits close to the summit of Slievenabawnoge, approximately 25 metres west of a cairn at 1,306 feet that marks a trigonometrical station, the kind of fixed reference point used in ordnance surveying. The site was recorded and compiled by archaeologists Geraldine Stout and Padraig Clancy, with notes last updated in July 2018. The combination of the barrow, the summit cairn, and the drystone wall makes for a layered landscape where different periods of human activity have quietly accumulated on the same ground.

Access to the hill involves negotiating a landscape that has changed considerably in recent years. The notes record that Slievenabawnoge has been planted with pine trees, which can alter both visibility and orientation considerably when moving through upland terrain. The monument itself sits just below the true summit, so following the slope upward toward the trigonometrical cairn and then looking roughly westward should bring the feature into view. The shallow hollow and low bank are subtle at ground level, so moving slowly and looking for the slight depression rather than a prominent mound is worthwhile. Overcast days, when low-angle light picks out surface irregularities, often make earthworks like this easier to distinguish from surrounding ground.