Sitting in quiet pasture in County Kildare, this ring barrow is considerably larger than the average example of its type, and its full extent only becomes apparent from the air. A ring barrow is a burial mound encircled by a ditch, or fosse, and an outer bank, and this one in Hallahoise measures roughly 60 metres across at its inner enclosure alone. Aerial photography has revealed a second, outer enclosure extending to approximately 155 metres by 116 metres, making the whole complex an unusually ambitious piece of prehistoric engineering for the Irish midlands.

The central mound itself is modest at the summit, only about 2 metres across at the top, but it sits on a natural hillock, which may have been deliberately chosen to give it added presence in the landscape. Someone has quarried into the eastern side at some point, and on the summit a small flagstone is exposed, possibly the capstone of a cist, the stone-lined burial box that prehistorical communities used to inter their dead. Whether a chamber survives intact beneath is unknown, though local tradition, recorded by Fitzgerald between 1899 and 1902, held that the mound was indeed chambered. The same source recorded the local name for the site as Dun-fin-yeen, a name that carries the suggestion of an older, now largely lost layer of meaning attached to this place. The curving field boundaries to the south and west may themselves be remnants of the original monument, quietly shaping the modern landscape without anyone necessarily registering why. A comparable barrow at Rathwalkin, also in Kildare, shares this unusual scale, suggesting that whatever tradition produced these monuments in this part of the country was operating with particular ambition.