Penywyrlod is the largest Neolithic long cairn to survive in the area of the Black Mountains and one of the largest in Wales. It measures 52m by 22.5m and stands a maximum 3m high. Situated at 260m above sea level the cairn is sited in a location typical for many Black Mountain long cairns, fairly high up in the foot-hills, close to what is now good agricultural land. The plan and features of the cairn suggest it is a member of the laterally-chambered, `dummy portal? group of Severn-Cotswold long cairns that are well represented in the Black Mountains area. It has been dated by Radio Carbon close to 3,900 cal BC and is thus a relatively early example.

The long cairn was first discovered in 1972 by a farmer who discovered human remains in a stoney mound being excavated for agricultural hard-core. A rescue excavation followed the discovery during September 1972. The quarrying removed a large part of the SE end of the cairn and exposed in the quarry face orthostats of a partially wrecked lateral chamber above which the body of the main cairn (small pieces of local sandstone) still rose by some 2m; the edge of a large capstone of a much larger and higher chamber 1m below the top of the cairn; two massive stone slabs representing the dummy portal and a small damaged cist. Excavation on the floor of the quarry also revealed another largely destroyed lateral chamber. A third lateral chamber was also examined in a much smaller quarry scrape further along the NE side of the cairn, together with sections of inner and outer revetment walls.

Louise Barker, June 2013, RCAHMW

Sources:
Briggs, C.S., 1997, An Inventory of the Ancient Monuments in Brecknock (Brycheiniog), The Prehistoric and Roman Monuments, Part i: Later Prehistoric Monuments and Unenclosed Settlements to 1000 A.D. RCAHMW. pp 38-40.

Britnell WJ & Savory HN 1984 Gwernvale and Penywyrlod: Two Neolithic Long Cairns in the Black Mountains of Brecknock. (Cambrian Archaeological Monographs No. 2)