That single fact, almost improbable given the long history of antiquarian interference with monuments of its kind, is perhaps what makes it so quietly compelling. Known as Miosgan Meva, or Maeve's Cairn, it sits on the summit of the mountain above the Cúil Irra peninsula in County Sligo, roughly sixty metres across and ten metres high, its flat-topped silhouette echoing the squat profile of the mountain beneath it. Folk tradition has long held it to be the burial place of Queen Maeve of Connacht, the formidable figure from the Ulster Cycle of Irish mythology, and whether or not that identification has any basis in prehistory, the name has stuck for centuries.

What archaeology does suggest is that the cairn is approximately five thousand years old, placing it broadly in the same period as the great Neolithic passage tombs at Newgrange and Knowth in the Boyne Valley. A passage tomb is a type of megalithic monument in which a stone-lined corridor leads to a burial chamber at the centre of a mound; whether Miosgan Meva follows this internal plan remains unknown. Because it escaped the attentions of eighteenth- and nineteenth-century treasure hunters who ransacked so many comparable monuments, its interior has never been disturbed, and its structure is a matter of informed speculation rather than established fact. What can be observed from the outside is more intricate than the smooth silhouette suggests. Large gneiss boulders protrude from the northern and north-eastern perimeter, possibly the remnants of a kerb. Five smaller stone concentrations, roughly eight to eleven metres across, abut the base of the main cairn to the east, south, and west. Two substantial stones, a prostrate limestone slab to the north and a gneiss erratic to the south, appear to have been deliberately placed as markers on a north-south alignment. A low earthen bank encircles the whole ensemble, kinking outward at each point to include the smaller cairns and marker stones within its circuit.

The cairn does not stand in isolation. Knocknarea is ringed by prehistoric remains: smaller satellite tombs and cairns cluster on the summit, hut sites and field walls descend the mountain's terraces, and two caves on the western flank have yielded evidence of Neolithic burials. At the foot of the mountain, the passage tombs of Carrowmore megalithic cemetery spread eastward across the lowlands of Cúil Irra. From the summit, the view extends far enough to take in Benbulben to the north-east, the Ballygawley and Ox Mountains, Cairns Hill, and, on clear days, well into counties Mayo and Donegal, connecting Miosgan Meva visually to a broader landscape dense with prehistoric monuments.