Qualla: Caernarfon Mithraeum

Caernarfon Mithraeum: Introduction

Sun, 24 May 2026 00:00:00 GMT

On 2 April 1958, contractors digging a sewer trench at the edge of Caernarfon hit stonework. They had cut straight through the anteroom of a Roman temple, slicing off the southeastern corner before anyone realised what they were destroying. The temple turned out to be a Mithraeum - one of perhaps a few dozen ever built in Britain, and the westernmost known on the entire Roman frontier. It was excavated the following August by George Boon for the National Museum of Wales. The mechanical excavator kept falling into the trench because the ground was so marshy.

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Caernarfon Mithraeum: The Cult of Mithras

Sun, 24 May 2026 00:00:00 GMT

Mithras was not a god the Romans found at home. He arrived from Persia, or possibly was reinvented in the eastern Mediterranean as something only loosely connected to the Persian original, and his cult spread across the empire from about the first century AD. It was a male-only i...

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Caernarfon Mithraeum: Three Temples on the Same Spot

Sun, 24 May 2026 00:00:00 GMT

What Boon's team excavated was actually three successive temples, each built on the foundations of the last. Phase I was a rectangular building 14.6 metres by 6.55, dated tentatively to the third century AD when Segontium was garrisoned by the Cohors I Sunicorum - a unit recruite...

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Caernarfon Mithraeum: The Last Light

Sun, 24 May 2026 00:00:00 GMT

Above the Phase III floor, archaeologists found a thin layer of soil - no more than sixty millimetres - and above that, a layer of burnt debris. The sequence tells a clear story. The temple was abandoned first. The Mithraic sculptures, which would have included the tauroctony and...

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Caernarfon Mithraeum: What You Can See Now

Sun, 24 May 2026 00:00:00 GMT

The Mithraeum itself is not visible today. After the excavation it was recorded, sampled, and backfilled, partly because the marshy ground that bothered the diggers in 1958 would continue to damage any exposed remains. What you can see is its larger neighbour: the fort of Segonti...

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