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Cross Ridge Dyke and Cairn on Twyn Hywel is a cross ridge dyke of unknown date located in Wales. The monument comprises an earthwork defence and an associated cairn positioned to exploit the site's natural topography on bedrock of the South Wales Upper Coal Measures Formation. The underlying geology of mudstone, siltstone and sandstone, interbedded with coal seams and ironstone deposits, has shaped the landscape and would have influenced both construction and settlement patterns in this region during antiquity.
Cross ridge dykes are linear defensive earthworks typically constructed across ridgelines or valley approaches to control movement and access across terrain. Without excavation or diagnostic artefacts, the precise chronology of Twyn Hywel's example remains uncertain, though such monuments were employed across multiple periods from later prehistory through the medieval era. The accompanying cairn may represent a contemporary ritual or funerary deposit, or a later addition to the site.
The monument is protected by Cadw, the Welsh Historic Monuments Service, under the reference GM456, ensuring preservation of this landscape feature for future study. The earthwork remains a significant record of early land division and territorial organisation in the Welsh uplands, even where its specific historical context has yet to be determined.
Cross Ridge Dyke & Cairn on Twyn Hywel is a scheduled monument protected by Cadw under reference GM456. View the official record →
Cross Ridge Dyke and Cairn on Twyn Hywel is a cross ridge dyke of unknown date located in Wales. It is designated a Scheduled Ancient Monument by Cadw under reference GM456.
Cross Ridge Dyke & Cairn on Twyn Hywel dates from the unknown period, and is classified as a cross ridge dyke. It is one of over 32,000 scheduled monuments protected across the UK.
Cross Ridge Dyke & Cairn on Twyn Hywel 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 GM456.
Several scheduled monuments lie within 10 km, including Tomen y Clawdd (4.7 km), The Pottery, Nantgarw (6 km), Five Round Barrows on Garth Hill (7.6 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Cross Ridge Dyke & Cairn on Twyn Hywel'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.
Cross Ridge Dyke & Cairn on Twyn Hywel 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.