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Llyn Dwr Cairn is a prehistoric cairn located in Wales and protected as a scheduled monument by Cadw under reference RD161. The monument sits upon bedrock composed of Ashgill Rocks, undifferentiated mudstones, siltstones and sandstones that formed during the Ashgill period of the Ordovician era. These fine-grained sedimentary deposits would have provided readily available stone-working material for the monument's construction.
The cairn represents a significant example of prehistoric burial or ceremonial practice in the Welsh landscape. Cairns of this type typically date to the Bronze Age or earlier prehistoric periods, though some are considerably older. Their construction involved the deliberate accumulation of stone to create a substantial mound, often erected over a burial chamber or in association with funerary or ritual activity.
The monument's survival to the present day, despite millennia of exposure to Wales' wet climate and agricultural land use, reflects both the robustness of stone construction and the protection afforded by its scheduled status. The Ashgill bedrock geology would have influenced both the initial selection of the site and the character of the building stone available to its creators.
Llyn Dwr Cairn is a scheduled monument protected by Cadw under reference RD161. View the official record →
Llyn Dwr Cairn is a prehistoric cairn located in Wales and protected as a scheduled monument by Cadw under reference RD161.
Llyn Dwr Cairn dates from the prehistoric period, and is classified as a cairn. It is one of over 32,000 scheduled monuments protected across the UK.
Llyn Dwr Cairn 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 RD161.
Several scheduled monuments lie within 10 km, including Dol-y-Fan Round Cairn (8.7 km), Bongam Bank Round Barrows (8.9 km), Cefnllys Medieval Settlement and Field Systems (9 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Llyn Dwr Cairn'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.
Llyn Dwr Cairn stands on Ashgill Rocks (Undifferentiated), bedrock that formed in the Ashgill. The rock here is mudstone, siltstone and sandstone.