It is believed to be the Welsh Atlantis, a lost land lying below the water at Cardigan Bay. For at least 800 years, tales have been told of the legend of Cantre’r Gwaelod, but evidence that it really existed has been scant.
Now, a medieval map depicting two islands off the Ceredigion coast provides some proof that the legend may be rooted in historical fact, according to a BBC report.
The discovery has been made by Simon Haslett, honorary professor of physical geography at Swansea University, and David Willis, Jesus professor of Celtic at the University of Oxford.
Haslett, who went in search of lost islands in Cardigan Bay while he was a visiting fellow at Jesus College, Oxford, explained that the two islands are clearly marked on the Gough map, held in the collections of the university’s Bodleian library.
The document is believed to be the earliest surviving complete map of the British Isles, dating from as early as the mid-13th century. The pair have published their findings in the journal Atlantic Geoscience.
Two islands are depicted, each about a quarter the size of Anglesey. One island is offshore between Aberystwyth and Aberdyfi and the other farther north towards Barmouth, Gwynedd.
Haslett told the BBC: “The Gough map is extraordinarily accurate considering the surveying tools they would have had at their disposal at that time.
“The two islands are clearly marked and may corroborate contemporary accounts of a lost land mentioned in the Black Book of Carmarthen.”
Cardiff University’s Welsh folklore expert, Dr Juliette Wood – who was not involved in this research – told the BBC the Black Book’s account was key to anchoring the story in Welsh myth.
“The Gough map may have its origins around 1280; shortly before that, around 1250, you have the Black Book of Carmarthen.”
Drawing on previous surveys of the bay and understanding of the advance and retreat of glaciers and silt since the last ice age about 10,000 years ago, Haslett and Willis were able to suggest how the islands may have come into existence and then disappeared again.
Haslett said: “I think the evidence for the islands, and possibly therefore the legends connected with them, is in two strands.
“Firstly, coordinates recorded by the Roman cartographer Ptolemy suggest that the coastline at the time may have been some eight miles further west than it is today.
“And, secondly, the evidence presented by the Gough map for the existence of two islands in Cardigan Bay.
He added that folk legends of being able to walk between lands now separated by sea could be a folk memory stemming from rising sea levels after the last ice age.
“However, legends of sudden inundation, such as in the case of Cantre’r Gwaelod, might be more likely to be recalling sea floods and erosion, either by storms or tsunami, that may have forced the population to abandon living along such vulnerable coasts.”
Wood added: “People, now as much as then, want to find a way of explaining things which seem simply unexplainable, especially during tough times.
“The romanticists among the Celtic population want to find meaning and a belief system to make sense of the current hardships.”
Haslett, however, warned that his findings could have more bearing on the future than the past.
“These processes didn’t happen just once, they’re still ongoing,” he said.
“With rising sea levels and more intense storms, it’s been suggested that people living around Cardigan Bay could become some of Britain’s first climate change refugees, within our lifetimes.”
