A massive oval roofstone, four metres long and nearly three metres wide, sits on a broad Waterford plateau as it has for several thousand years, balanced on a septal-slab and a backstone with a cushion-stone wedged between stone and capstone to hold the whole arrangement steady. What makes the Ballynageeragh portal tomb quietly puzzling is the absence of its portal-stones, the tall paired uprights that normally frame the entrance of this type of megalithic structure and give the monument its name. The sidestones survive, the roofstone is intact, and the tomb still faces south-west, but the defining architectural feature is simply gone.

Portal tombs, sometimes called dolmens, are among the earliest monumental structures in Ireland, generally dated to the Neolithic period and thought to have served as communal burial sites. When this one was investigated and conserved in 1939 and 1940, the chamber yielded cremated bone, flint, and charcoal, the residue of funerary activity reaching back millennia. The site had attracted attention long before that work: George Victor Du Noyer recorded it in the 1860s, and it appeared again in a publication by Atkins in 1896. Later surveys by Ó Nualláin and Harbison placed it within the broader picture of Irish megalithic architecture. The roofstone alone, at seventy centimetres thick and weighing considerably more than a casual glance suggests, would have required considerable organisation to raise and position, which is part of what makes the missing portals an open question rather than a settled one.