The Mysterious Man-made Caves Built by Iron Age Cornish Settlers

Fogous, a term derived from the Cornish word for cave, ‘ogo’, are a puzzling feature of the landscape for tourists, historians and archaeologists alike. There are nine known manmade cave systems in the county of Cornwall, all dating back to Iron Age settlers. Other local terms for these peculiar caves are fuggy holes or vugs.


Unlike the Neolithic and Bronze Age stone circles, barrows, enclosures, and settlements, Fogous appear to serve no purpose whatsoever, despite the huge amount of care and effort that would have gone into their construction.


Analysis of the most intact fogous found, revealed that the process of building these tunnels and caves began with the excavation of deep trenches sited near to a settlement, which were then lined with rock slabs or dry-stone walls, capped with more lintel stones and then covered entirely with soil, rubble and turf.


Likened to the souterrains found in Scotland, Ireland, Brittany and Normandy, these underground caverns and tunnels, created entirely by prehistoric man, are only found in the county of Cornwall and nowhere else in England. It almost reinforces the notion that true Cornish people have more in common with the inhabitants of North-West France than their English cousins.


One of the most intact and well-preserved fogous is found on the Lizard Peninsula, close to the Trelowarren Estate. The Halliggye Fogous is well off the tourist trails. Despite there being some parts of the structure visible above ground betraying its location during the Iron Age, the entrance would not be easily found.


Example tunnel with modern steps for visitors
Similar modern steps are now present at Halliggye

Access begins by stepping down modern stairs into a narrow trench, lined with sheer stone-faced walls. As you descend, the passageway narrows significantly and the temperature drops by a considerable amount. The complex follows a roughly upside-down T shape, with one tunnel branching off the entrance passage.


The straight tunnel is large enough to comfortably move about in. It runs for 8.4 metres down to a crawlspace of another 4 metres at the end. At the start of the crawl space, you are greeted by an impressive doorway comprising two wide gate stones capped with another huge rectangular boulder. To the left of this gateway, is a second tunnel that branches off in a massive curve and spans more than 27 metres. Deep in this eerie and inaccessible space, is a second crawlspace that juts off to the left and is preceded by a stone lip embedded into the floor to trip unsuspecting visitors.


Over the years, there have been a number of excavations, studies, analyses and theories as to the possible purpose for building these underground structures. That does mean, of course, that no one can be certain of the original contents found in the tunnels. Ancient settlers were resourceful and renown for reusing building materials over the centuries, removing archaeological remains and artefacts from the Neolithic times onward. One burial cairn in Capel Garmon, near Snowdonia, had all Bronze Age remains removed so that it could be used as a stable in the 19th century. Stones from some abandoned Cornish roundhouses were also moved to reinforce animal enclosures or defences.


Burial Cairn at Capel Garmon, later used as a stable in the 19th Century
Burial Cairn at Capel Garmon, later used as a stable in the 19th Century

The absence of archaeological artefacts has made it particularly difficult to determine the use for the caves. The Reverend Richard Polwhele, recorded his findings on entering the Halliggye Fogou in 1803. He maintained that the tunnels contained urns but if they were present during his excavations, they are not there now, nor is there any record of them being stored elsewhere.


Later analysis of the tunnel detritus revealed no evidence of cremation ashes or bone, no midden waste, pottery sherds, metal deposits or grains, which only tells us that if the tunnels were once used as a cold storage place, they were subsequently cleaned to a high degree.


Another common hypothesis for their purpose is as a hiding place for the settlers from the threat of attack. Since the tunnels are commonly cold and damp, with cramped and intolerable conditions within, that is a difficult assumption to swallow. If they were to go to all the trouble of building an Iron Age panic room, why would they make them so inaccessible and unpleasant? For those with little knowledge of the county of Cornwall, natural caves are abundant within the craggy cliffs of the coastline, yet there are fogous close enough to the coastal caves to render building them redundant.


The fact that some of the fogou entrances were visible from the surface rather than being wholly hidden, would make the idea that they could have been used as secret hoard tunnels for precious goods and metals less likely.


When the most obvious reasons are rendered improbable, it leaves archaeologists with their usual cover-all theory; that the tunnels were built for ceremonial use. Since there are no records, nor concrete evidence to support religious practices in Britain from before the Roman occupation, we can only hazard an educated guess based on the objects found and the prevalence of cultural folklore and mythology passed through the ages via the spoken word.


A senior archaeologist for Historic Environment Scotland, Richard Strachan, who manages the souterrains under the Scottish group’s purview, suggests that the fogous could have had many uses over the years. “I think they’re multipurpose, maybe seasonal as well,” Strachan states. “Maybe you use them for storage, then when you don’t need them for storage, you use them for ceremony.”


The theory is strengthened by the more recent excavations at Boden, where an S-shaped fogou was uncovered alongside an entire Bronze Age settlement. Analysis dated the construction of the round houses, and pot sherds found within, to around 1400BCE. Similar studies discovered that the settlement was abandoned some 300 years later, yet the S-shaped tunnels were created long after, around 400 BCE. The new builders took great care to wind the fogous around the abandoned huts, leaving them intact.


If their intention was to create a cold store, why choose a site that already had community buildings present? Why, after all the effort of constructing a complex tunnel system that avoided the demolition of those huts, would they leave them uninhabited? It seems most likely that a ritualistic or religious reason prevented them from desecrating the site, especially since evidence suggests that the tunnels were also closed some 500 years later in an equally precise way.


James Gossip, archaeologist and British prehistory expert, and his team of volunteers, studied the fogou at Boden every summer since 2003. Their findings revealed that early Iron Age pottery was placed on the floor, carved out from the bedrock, the capstones removed and the tunnels deliberately back-filled with rock and soil from the surrounding area. This ‘closing’ of the tunnels is also visible at souterrains elsewhere.


Perhaps we will never know for sure why these dark, narrow passages were built, or whether the ceremonial usage is correct, but we can and do know much about human nature. If we go to the trouble of building a functional space, we endeavour to make it fit for purpose. None of the tunnels are easy to access, some have highly acidic soils making food storage difficult and there is no evidence of them being used for funerary practices.


Could it be that they were part of some sort of endurance test? The crawl spaces would have been extremely uncomfortable, pitch dark, damp and cold, in short, they would most probably be best avoided by the average person.


We may never know for sure why these caves and passages were created and hidden beneath tonnes of turf and topsoil, but they do add to the mystery of Cornwall as a whole and make for an excellent day out for visitors to the region.


All I know is that I am way too cowardly to venture inside one, not because I think they may be infested with Cornish Piskies or that a gateway might open, unleashing evil spirits to drag me into the Underworld, but because my claustrophobia and asthma might get the better of me. One thing is certain; Iron Age people were far tougher than I will ever be.




My sincerely gratitude goes to the brave people who did squeeze themselves into the tunnels and returned to describe their experiences so that I could remain a coward.

Amanda Ruggeri, BBC Great Britain (June 2016)

E.V. Clark et al – The Fogou of Lower Boscaswell, Cornwall.

Dave Hamilton – Wild Ruins BC

Cornishbirdblog.com

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