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Offa's Dyke: Caeau-Gwynion Section is an early medieval linear earthwork in Wales, constructed as a substantial boundary across the border landscape. Built in the late 8th century, the dyke follows the natural contours of the surrounding terrain, with the Millstone Grit bedrock beneath the site providing a resistant sandstone, siltstone and mudstone foundation typical of the Namurian geological period. This geology shaped both the dyke's construction and its long-term survival.
The Caeau-Gwynion section represents a carefully engineered stretch of Offa's Dyke, taking advantage of the local topography to maximise its defensive and demarcation effectiveness. The earthwork's scale and ambition demonstrate substantial resources and organisational capacity under King Offa of Mercia, whose reign saw the dyke's construction as a frontier marker and control mechanism.
Now protected by Cadw under reference DE133, this section of the dyke remains one of the most significant early medieval monuments in Britain. The preservation of the earthwork across its original course allows visitors and researchers to understand the engineering decisions and territorial intentions of 8th-century frontier construction, visible across the Welsh landscape as a tangible boundary between two distinct political regions.
Offa's Dyke: Caeau-Gwynion Section is a scheduled monument protected by Cadw under reference DE133. View the official record →
Offa's Dyke: Caeau-Gwynion Section is an early medieval linear earthwork in Wales, constructed as a substantial boundary across the border landscape. It is designated a Scheduled Ancient Monument by Cadw under reference DE133.
Offa's Dyke: Caeau-Gwynion Section 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.
Offa's Dyke: Caeau-Gwynion Section 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 DE133.
Several scheduled monuments lie within 10 km, including Offa's Dyke: section 1300yds (1190m) long, N from Careg-y-Big (6.9 km), Offa's Dyke: section 200yds (180m) long, at Careg-y-Big (7.4 km), Offa's Dyke: section 250yds (230m) long, S of Careg-y-Big (7.7 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Offa's Dyke: Caeau-Gwynion Section'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.
Offa's Dyke: Caeau-Gwynion Section stands on Millstone Grit Group [See Also Migr], bedrock that formed in the Namurian. The rock here is mudstone, siltstone and sandstone.