1. Two summit cairns, each having a more recent and diminuative cairn raised upon it.
(source OS 495 card: SN79SE1)
J.Wiles, RCAHMW, 04.02.2002.

2. "Carn Gwilym. Although marked as a single cairn on the Ordnance sheet, there are here two cairns, 60 feet apart. They stand on the summit of Mynydd Hyddgen [On the elevated plateau of Mynydd Hyddgen, of which the point occupied by this cairn is the summit, Owen Glyndwr defeated an English force in A.D. 1401 (see nprn 402310)], an outlying height of Plynlymon, midway between the sources of Nant y Garn and Nant Lluest fach. They are each 20 feet in height; of rough construction, the stones being piled into a mass without any signs of regular courses. No stones similar to those used in the building of these cairns are to be seen anywhere around; none are scattered about from which they could now be erected, and none are of a size larger than one man could carry hither. Of the carneddau of the Plynlymon district Carn Gwilym is probably the best preserved. Visited, 6th May, 1910." RCAHMW Montgomeryshire Inventory 1911, no.919.
B.A.Malaws, RCAHMW, 24 October 2006.

3. Two large Bronze Age cairns, NPRNs 289720 and 289723, on top of a summit. Two smaller satellite cairns, NPRNs 289722 and 289726 lie to the east of the main cairns. The larger cairns have had more recent cairns erected on top of them, NPRNS 289721 and 289724) J.J. Hall, Trysor, 11 September 2006.