That detail, recorded by a local writer around 1850, goes some way to explaining the state of what survives today: a badly damaged megalithic structure, perhaps five thousand years old, standing about forty metres west of a stream that cuts southward through a steep-sided valley.

Portal tombs, sometimes called dolmens, are among the most visually distinctive of Ireland's prehistoric monuments. They typically consist of two tall upright portal stones framing a chamber entrance, covered by one or more large capstones. At Tubbrid, the chamber measures at least two and a half metres in length and opens to the north-east, but only the western portal stone and two adjoining sidestones remain standing, the portal leaning outward at a pronounced angle. The chamber was originally covered by two roofstones. The northern of these, according to Fogarty's account from around 1850, was blasted with powder and now lies shattered into at least three pieces, tilted to the east and partly resting on the southern roofstone, which itself stands at an awkward angle within the chamber, oversailing the sidestones. The entire eastern side of the monument is gone, though what may be a fallen sidestone protrudes from beneath the roofstones at the south. A nineteenth-century sketch held in the National Library of Ireland, drawn from the north-east, shows the monument before the full extent of its deterioration: the portal stone already leaning, but the northern roofstone still whole. By the time Borlase catalogued it in 1897 and Powell noted it in 1941, it had settled into the fragmented condition visible today. The act of blasting the capstone, presumably to clear the stone for agricultural or building use, was not unusual in rural Ireland during the eighteenth and nineteenth centuries, when prehistoric monuments were frequently dismantled without record or ceremony.