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Carn Biga is a prehistoric round cairn situated on Pumlumon Fawr, the highest point in the Cambrian Mountains of Wales. The monument consists of a circular mound of stacked stone, typical of cairns constructed during the Bronze Age to mark burial sites or ceremonial locations. Its position on this exposed upland location reflects the ancient use of high ground for monuments of spiritual or commemorative significance.
The cairn sits upon bedrock composed of Ashgill Rocks, a formation of mudstone, siltstone and sandstone laid down during the Ordovician period. This glacially scoured landscape, with its shallow soils and outcrops of dark stone, would have provided readily available material for construction. The harsh mountain environment and commanding altitude suggest the monument held considerable importance to the communities that built it.
Carn Biga is protected by Cadw, the Welsh heritage authority, under reference MG110, recognising its archaeological significance. Its survival on Pumlumon Fawr, where it has endured centuries of upland weather and use, testifies to the durability of cairn construction. The monument remains an important marker of prehistoric activity in the Cambrian Mountains.
Carn Biga, Pumlumon Fawr/Plynlimon is a scheduled monument protected by Cadw under reference MG110. View the official record →
Carn Biga is a prehistoric round cairn situated on Pumlumon Fawr, the highest point in the Cambrian Mountains of Wales. It is designated a Scheduled Ancient Monument by Cadw under reference MG110.
Carn Biga, Pumlumon Fawr/Plynlimon dates from the prehistoric period, and is classified as a round cairn. It is one of over 32,000 scheduled monuments protected across the UK.
Carn Biga, Pumlumon Fawr/Plynlimon is a Scheduled Ancient Monument, legally protected by Cadw — the body responsible for designating and safeguarding heritage sites in Wales. The official designation reference is MG110.
Several scheduled monuments lie within 10 km, including Cairns on Pen Plynlimon-Arwystli (2.6 km), Nant yr Eira Prehistoric Copper Mines & 19th Century Lead Mine (2.6 km), Cairn on Pen Lluest-y-Carn (4.4 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Carn Biga, Pumlumon Fawr/Plynlimon's history, each drawn from the record and mapped to the exact spot:
Every location is different. Not every section appears for every place, only what the historical record actually holds turns up in a report.
Carn Biga, Pumlumon Fawr/Plynlimon stands on Ashgill Rocks (Undifferentiated), bedrock that formed in the Ashgill. The rock here is mudstone, siltstone and sandstone.