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Twyn Bryn Glas is a prehistoric round cairn situated in Wales on bedrock composed of Dinantian limestone, sandstone and argillaceous rocks. The monument sits on geology that was laid down during the Mississippian period, when this region lay beneath tropical seas. Round cairns of this type were constructed as burial monuments, typically during the Bronze Age, and would have served as enduring markers of the dead across the upland landscape.
The cairn's construction took advantage of the stone-rich terrain afforded by the underlying Dinantian formation. Builders gathered surface stones to heap over a central burial, creating a durable mound visible from considerable distances. The limestone bedrock and associated stone resources meant that such monuments could be made substantial and long-lasting, remaining recognisable features of the Welsh countryside thousands of years after their construction.
Twyn Bryn Glas is protected as a scheduled ancient monument by Cadw under reference GM561, ensuring its preservation for future study. The monument contributes to understanding Bronze Age burial practices and settlement patterns in Wales, whilst its survival testifies to the enduring quality of these simple yet effective stone structures built upon the resilient Dinantian geology.
Twyn Bryn Glas round cairn is a scheduled monument protected by Cadw under reference GM561. View the official record →
Twyn Bryn Glas is a prehistoric round cairn situated in Wales on bedrock composed of Dinantian limestone, sandstone and argillaceous rocks. It is designated a Scheduled Ancient Monument by Cadw under reference GM561.
Twyn Bryn Glas round cairn 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.
Twyn Bryn Glas round cairn 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 GM561.
Several scheduled monuments lie within 10 km, including Iron Tram Bridge, Robertstown (8.1 km), Tramroad East of Robert's Town Bridge, Aberdare (8.2 km), Gwersyll (8.7 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Twyn Bryn Glas round cairn'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.
Twyn Bryn Glas round cairn stands on Dinantian Rocks (Undifferentiated), bedrock that formed in the Mississippian. The rock here is limestone with subordinate sandstone and argillaceous rocks.