Eighty-five metres to its north, however, sits a far quieter and considerably more ruined passage tomb that receives a fraction of the attention. It is easy to overlook, and that overlooking is itself part of the story. A low circular cairn, roughly ten to twelve metres across and only a metre high, encloses what was once a cruciform passage tomb, the kind of megalithic structure in which a long stone passage leads to a central chamber with three recesses branching off it. Only nine upright slabs, orthostats, of limestone and gneiss remain standing in place, the chamber and passage long since collapsed and open to the sky. One intriguing detail sets this tomb apart even among ruined examples: it has been suggested that the cairn may never have been tall enough to cover the top of the chamber at all, which would make it architecturally unusual rather than simply degraded. Encircling the cairn at a distance of about five metres is a concentric limestone bank, thirty metres in diameter, adding a further layer of deliberate geometry to the monument.

The tomb suffered the attentions of Richard Chamber Walker, a local landowner and antiquarian who disturbed several monuments on Knocknarea in the early nineteenth century. His investigations, however loosely that word applies to what was more likely enthusiastic digging, yielded finds recorded later by Wood-Martin in 1895: burnt human and animal bones, along with small round unperforated beads, possibly of stone. The human remains confirm the site's funerary purpose, as would be expected of a Neolithic passage tomb, while the animal bones and beads suggest the kinds of ritual deposit that archaeologists associate with these monuments across Ireland. The early OS six-inch maps marked the site simply as "Carn", a nod to its visible presence on the summit even as its identity as a passage tomb went unremarked.