The bog has done what bog does: it has swallowed things whole. A wedge-tomb, the characteristic megalithic burial form of the Early Bronze Age, is largely buried in it on the southern slopes. Turf-cutting has exposed a pre-bog hut foundation nearby. And scattered across both sides of the small river that threads the valley floor are stone enclosures, a cairn, a possible cist grave, a standing stone, and field boundaries that predate the peat itself, or may do; the qualification matters, because the valley refuses to yield certainties.

The two circular enclosures on the northern bank are modest, almost self-effacing. The larger measures 9.5 metres in internal diameter, its bank of earth and stone no more than 15 centimetres high and thickly turf-covered; there is a possible entrance at the east-south-east, marked by a single stone set on edge. The smaller is just 5 metres across, enclosed by an equally low bank. Neither announces itself. Nearby sits a large irregular cairn, roughly 25 metres by 19.5 metres, with some stones set deliberately upright though in no recognisable arrangement, and 4.5 metres to its east, a possible cist, the type of small stone-lined box grave associated with Bronze Age burial, its five inward-leaning slabs open to the east and missing any capstone. Whether these features are contemporary with one another, or with the wedge-tomb across the river, cannot be established from surface examination alone. What the standing stone and the wedge-tomb do suggest, taken together, is Early Bronze Age activity in this valley, and it is at least possible that some of the field walls, now surviving as low turf-covered rows of stone, belong to the same broad period, predating the growth of the peat that eventually covered them. J. Cuppage documented this cluster of monuments in the 1986 Corca Dhuibhne archaeological survey, and the picture he assembled is one of accumulated, overlapping use rather than any single moment of occupation.

The northern side of the valley was reclaimed and enclosed again in the modern era; the first edition Ordnance Survey map, dating from the early nineteenth century, already shows this field system in place, superimposed on the ghost of an earlier one beneath it. Walking the moorland to the north, east, and south of those modern fields, it is still possible to trace disused boundaries, rows of stones some upright, some collapsed into low banks, that belong to neither the modern enclosure nor confidently to the Bronze Age, but somewhere in between. An Gleann Mór is that kind of place: less a site than a palimpsest, each layer of human activity partially legible, partially obscured, and connected to the others by inference rather than proof.