The tunnels are in remarkable condition despite being several centuries old — but no one knows why they’re there (Image: English Heritage)
Deep within the countryside of one of the UK’s most beautiful counties, a series of ancient and enigmatic underground caves continue to baffle experts. These thousands-of-years-old structures, known as fogous (pronounced foo-goos), are unique to this region and their purpose remains shrouded in mystery.
These subterranean passages and caves lead to unknown destinations, despite it being likely that they served a crucial role in the distant past – even if we may never fully understand what that was.
Among the most well-preserved ancient settlements in Cornwall is Carn Euny, located at Sancreed, near Penzance. This site, inhabited from the Iron Age through to late Roman times, houses one of these perplexing fogous.
The village features the remnants of stone dwellings dating back to the second to fourth century AD, with walls reaching up to a metre high in some areas, still impressively intact. The village’s most captivating feature lies at its core – a stone-walled underground passage.
Fogous, the Cornish term for cave, typically comprise a buried stone wall, usually corbelled, narrowing towards the top and topped with stone slabs, reports .
Inside the mysterious fogou at Carn Euny (Image: English Heritage)
This peculiar type of Iron Age monument is exclusive to the far west of Cornwall, although similar structures have been discovered elsewhere. Despite their long-standing presence, very little is known about their origins or purpose.
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The foundations of the caves are believed to have remained largely unchanged, resembling their original state when they were part of the surrounding settlements. The village of Carn Euny was first unearthed by tin miners in the early 19th century, but it wasn’t until 1964-72 that extensive excavations took place.
Over time, the site has suffered damage due to stone-robbing and farming activities, making the overall layout difficult to discern. However, archaeologists estimate that there were at least ten houses from various periods of occupation, dating back to the Iron Age.
An aerial view of Carn Euny village (Image: English Heritage)
Carn Euny’s fogou is one of two such structures under the care and protection of English Heritage. The largest and best-preserved fogou is Halliggye Fogou, located on the Lizard peninsula.
Experts believe there are only about fifteen of these ancient structures in existence, with similar ones known as souterrains found in Ireland, Scotland, and France. Halliggye Fogou, another site maintained by English Heritage, is thought to date back to the fifth or fourth century BC.
Halliggye Fogou was once part of a small farming community, likely inhabited until the end of the Roman period. With its stone walls and roof, this complex of fogou passages is the largest and best-preserved of several enigmatic underground tunnels associated with Cornish Iron Age settlements.
Visitors are invited to explore the mysterious and narrow passages of the fogou, a hidden world nestled within a type of settlement known as a round. A round is a small enclosure defined by banks and a ditch, typically housing small timber or stone houses, round or oval in plan, dating back to ancient times.
Excavations have revealed that Halliggye, the site where the fogou is located, has been occupied since the fourth or fifth century, making it one of the earliest known examples of this kind of settlement. The fogou is situated in the north-west part of the round, its entrance accessible through a short open passage with its original sloping floor.
The passages of the fogou run entirely underground, comprising several different sections built at various times, as discovered during excavations in the 1980s. The purpose of fogous has sparked much debate and numerous excavations over the years.
Win Scutt, properties curator in the west for English Heritage, shared with CornwallLive three main theories about the possible uses of these intriguing caves. He suggested they could have served as a refuge during troubled times, a cold store or cellar for food storage, or even held some sort of ritual significance.
However, Mr Scutt considers the latter theory to be the least likely.
The detailed plan for Halliggye Fogou (Image: English Heritage)
Win Scutt, an expert on ancient structures, shed light on the mysterious underground constructions known as fogous. “They are an Atlantic phenomenon if you like,” he said.
“Fogou is a Cornish name but these types of structures have been found elsewhere and in Ireland they use a French word, souterrain, which means under the ground. They have also been found in Scotland.”
Scutt believes that Cornwall’s unique geology and culture played a role in the creation of these structures: “I think one of the reasons they are in Cornwall is because they have adapted to the conditions and the geology. If you’re in Wiltshire, for example, you don’t easily have the stone required, but I also think it was a cultural thing people did in West Cornwall, certainly in the Iron Age and through the Roman period.”
However, he noted that the ‘true’ purpose of the fogous remains elusive, largely due to inadequate archaeological investigation. He added: “But we don’t really know much more than that about what they are for and that is partly because they haven’t been properly excavated under modern conditions and even then it would be difficult to determine.”