Cairn situated on a prominent SW to NE aligned ridge of volcanic rock crossing the summit of Mynydd Rhiw. This is one of six cairns located on the mountain, this and four others (NPRNs 308047, 308048, 302262, 421096) are sited along the same ridge and the sixth (NPRN 302257) to the west.

The cairn is situated just 9m south of and below a more prominent cairn (NPRN 308047). It comprises a low spread of stone 14m in diameter and 0.5m high into which a recent structure has been constructed. Around the north-west edge of the cairn, a series of stones may represent the original kerb.

This cairn appears to have been used as a sighting point on the line of the Parish Boundary (NPRN 421094). The boundary runs up and changes direction at the cairn and there is some suggestion that parts of the parish boundary may have earlier antecedents.

Louise Barker, RCAHMW, July 2015

Sources:
RCAHMW, 1964 Caernarfonshire vol III. A Survey and Inventory by the Royal Commission on the Ancient and Historical Monuments of Wales. (Mon. No. 1753)
OS495card; SH22NW2
RCAHMW AP965034/52; 965122/41