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Gelli Diogyn Hillfort is a prehistoric fortified settlement located in Wales, sited on bedrock composed of Arenig Rocks of the Arenigian period. These underlying strata of mudstone, siltstone and sandstone provided the geological foundation upon which the hillfort was constructed. The monument is protected and recorded by Cadw, the Welsh Historic Monuments service, under reference CM293.
Hillforts of this type were typically constructed during the Iron Age, though some may have had earlier origins in the Bronze Age. They served as defended settlements, ritual centres or places of refuge, their elevated positions offering both practical defensive advantage and visibility across the surrounding landscape. The choice of location at Gelli Diogyn would have provided commanding views of the local terrain.
The hillfort comprises defensive earthworks characteristic of Iron Age fortifications, with ramparts and ditches arranged to create secure enclosures. The specific layout and construction methods reflect the engineering knowledge and social organisation of the prehistoric communities who built and inhabited the site. As a protected monument, Gelli Diogyn remains an important archaeological record of Wales's prehistoric past.
Gelli Diogyn Hillfort is a scheduled monument protected by Cadw under reference CM293. View the official record →
Gelli Diogyn Hillfort is a prehistoric fortified settlement located in Wales, sited on bedrock composed of Arenig Rocks of the Arenigian period. It is designated a Scheduled Ancient Monument by Cadw under reference CM293.
Gelli Diogyn Hillfort dates from the prehistoric period, and is classified as a hillfort. It is one of over 32,000 scheduled monuments protected across the UK.
Gelli Diogyn Hillfort 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 CM293.
Several scheduled monuments lie within 10 km, including Llan-Marlais Round Barrow (5.4 km), Llanddewi Gaer (7.5 km), Caerau Gaer (7.8 km).
This page is just one thread. A full Aubrey report pulls together 13 strands of Gelli Diogyn Hillfort'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.
Gelli Diogyn Hillfort stands on Arenig Rocks (Undifferentiated), bedrock that formed in the Arenigian. The rock here is mudstone, siltstone and sandstone.