An oval earthen mound, modest in every dimension, roughly four and a half metres east to west, three and a half metres north to south, and barely half a metre in height, it would be easy to step over without registering it as anything deliberate at all. Yet it is a classified National Monument, No. 153, held in state ownership, and documented as a distinct archaeological site in its own right.

Knocknarea is already one of the more densely layered prehistoric landscapes in Ireland, and this mound sits within that cluster rather than apart from it. Recorded by Stefan Bergh in 1995 as site 4 within his survey of the mountain's monuments, it lies just seven metres north-east of another feature classified as a possible passage tomb, itself still not fully understood. Passage tombs, in their more familiar form, are prehistoric megalithic structures built to receive the dead, typically consisting of a stone-lined corridor leading to a chamber covered by a large mound of earth or stone. Whether this smaller, apparently earthen oval shares any functional or chronological relationship with its neighbours is not established, and its composition, lacking the obvious stonework of a passage tomb, leaves its original purpose open. That ambiguity is itself part of what makes it worth attention: not everything on a site as celebrated as Knocknarea has been neatly explained.