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Domen Seba (also known as Y Tomen Fawr) is a medieval motte castle situated in Wales. The mound rises from bedrock composed of Ashgill rocks—mudstone, siltstone and sandstone formations laid down during the Ashgill period. This underlying geology would have provided a stable foundation for the earthwork's construction, though the softer mudstone and siltstone would have required careful management to prevent erosion of the mound's slopes.
The monument represents a typical Norman motte design, consisting of an artificial mound that once supported a timber or stone superstructure. The site's survival owes much to its protected status under Cadw, the Welsh heritage organisation, which holds it under reference CM020. Such mottes were constructed across Wales during the medieval period as symbols of military authority and territorial control, serving as strategic strongholds within the wider landscape.
The immediate topography and underlying bedrock geology at Domen Seba would have influenced both its original construction and subsequent preservation. The Ashgill rocks, exposed across much of the surrounding terrain, shaped not only this monument but the broader defensive strategies of medieval Wales, as builders adapted their fortifications to local conditions and available materials.
Domen Seba (or Y Tomen Fawr) Castle Mound is a scheduled monument protected by Cadw under reference CM020. View the official record →
Domen Seba (also known as Y Tomen Fawr) is a medieval motte castle situated in Wales. It is designated a Scheduled Ancient Monument by Cadw under reference CM020.
Domen Seba (or Y Tomen Fawr) Castle Mound dates from the medieval period, and is classified as a motte. It is one of over 32,000 scheduled monuments protected across the UK.
Domen Seba (or Y Tomen Fawr) Castle Mound 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 CM020.
Several scheduled monuments lie within 10 km, including Nant-Gronw Round Barrows (5.6 km), Crug Ieuan Round Barrow (5.9 km), Garreg Wen Standing Stone (6 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Domen Seba (or Y Tomen Fawr) Castle Mound'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.
Domen Seba (or Y Tomen Fawr) Castle Mound stands on Ashgill Rocks (Undifferentiated), bedrock that formed in the Ashgill. The rock here is mudstone, siltstone and sandstone.