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Cwm-Clais Castle Mound is a medieval motte situated in Wales, occupying the coalfield landscape of South Wales. The monument rises from bedrock of the Upper Coal Measures Formation, a geology of mudstone, siltstone and sandstone interspersed with coal seams and ironstone typical of the Westphalian period. This dense, layered bedrock would have provided a firm foundation for the earthwork's construction, whilst the ferricrete bands within it may have influenced water drainage across the mound.
The motte represents a common form of early medieval fortification, consisting of a raised earthen mound that would have supported timber or stone defensive structures. Mottes in South Wales frequently served as administrative and military centres during the Anglo-Norman consolidation of the region, their elevated positions commanding strategic views across surrounding valleys and settlement patterns.
The monument is protected by Cadw, the Welsh Historic Monuments service, under reference GM289. The site's survival within an industrialised coalfield region reflects the importance assigned to its preservation as evidence of the medieval occupation and defence of the Welsh landscape, prior to the intensive mineral extraction that would later transform the South Wales terrain.
Cwm-Clais Castle Mound is a scheduled monument protected by Cadw under reference GM289. View the official record →
Cwm-Clais Castle Mound is a medieval motte situated in Wales, occupying the coalfield landscape of South Wales. It is designated a Scheduled Ancient Monument by Cadw under reference GM289.
Cwm-Clais 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.
Cwm-Clais 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 GM289.
Several scheduled monuments lie within 10 km, including Half Moon Camp (6.2 km), Margam Medieval Bath House (6.2 km), Hen Eglwys Chapel and Defended Enclosure (6.4 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Cwm-Clais 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.
Cwm-Clais Castle Mound stands on South Wales Upper Coal Measures Formation, bedrock that formed in the Westphalian. The rock here is mudstone, siltstone, sandstone, coal, ironstone and ferricrete.