© Mapbox · © OpenStreetMap contributors · Boundary data © Cadw
Clawdd-Mawr is an early medieval linear earthwork located in Wales and protected by Cadw under reference CM110. The monument consists of an elongated earthen bank or ditch system characteristic of early medieval boundary works, constructed across terrain underlain by Ashgill Rocks—a formation of mudstone, siltstone and sandstone deposited during the Ashgill period of the Ordovician. The underlying geology, with its mix of relatively soft sedimentary rocks, would have presented workable ground conditions for the labour-intensive excavation and construction of such a frontier work, though the varying hardness of the strata may have affected the precision and durability of the earthwork's profile over the centuries.
The linear form suggests a demarcation of territorial or administrative boundaries during the early medieval period, a common function for such works across Wales and the Welsh Marches. These earthworks served to delineate kingdoms, control movement, and assert authority over disputed or marginal lands. The survival of Clawdd-Mawr into the present day, despite ploughing, erosion and vegetation growth, reflects the substantial labour invested in its original construction and the persistence of the boundary it marked.
Clawdd-Mawr is a scheduled monument protected by Cadw under reference CM110. View the official record →
Clawdd-Mawr is an early medieval linear earthwork located in Wales and protected by Cadw under reference CM110.
Clawdd-Mawr dates from the early medieval period, and is classified as a linear earthwork. It is one of over 32,000 scheduled monuments protected across the UK.
Clawdd-Mawr 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 CM110.
Several scheduled monuments lie within 10 km, including Defended Enclosure 300m W of Pen y Gar (5.8 km), Cross-Incised Stone in Churchyard (5.8 km), Ffos-y-Maen Standing Stone (6.1 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Clawdd-Mawr'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.
Clawdd-Mawr stands on Ashgill Rocks (Undifferentiated), bedrock that formed in the Ashgill. The rock here is mudstone, siltstone and sandstone.