A Medieval Map Has Revealed the Location of a Lost ‘Atlantis,’ Study Says

The lost kingdom of Cantre’r Gwaelod in Wales is said to have sunk beneath the waves, and now researchers may have identified it.
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Gough Map. Image: Bodleian Library
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For centuries, rumors have circulated about an ancient kingdom called Cantre’r Gwaelod that once existed in Wales’ Cardigan Bay, before it sank beneath the waves to become the basis for a legendary “Welsh Atlantis.”  

The tales of Cantre’r Gwaelod have shifted over the years, with some saying that a maiden neglected to stop a well from overflowing over the lands, while later tales blame a drunken gatekeeper who failed to oversee the dykes. Legend has it that the bells of the sunken kingdom’s church can still be heard on quiet evenings.


Now, a pair of researchers present new evidence that two islands did once exist in the bay, based on an analysis of a medieval map, folkloric accounts, field studies, and geological surveys. Led by Simon Haslett, honorary professor of physical geography at Swansea University in Wales, the work demonstrates that “the existence of the ‘lost’ islands is considered plausible and offers a possible insight into the post-glacial coastal evolution of Cardigan Bay,” according to a study published in Atlantic Geoscience.

“This study investigates historical sources, alongside geological and bathymetric evidence, and proposes a model of post-glacial coastal evolution that provides an explanation for the ‘lost’ islands and a hypothetical framework for future research,” Haslett and co-author David Willis, Jesus professor of Celtic at the University of Oxford, wrote in the study. “Literary evidence and folklore traditions provide support in that Cardigan Bay is associated with the ‘lost’ lowland of Cantre’r Gwaelod.”

The study is the first work to fully investigate two mysterious islands that appear on the Gough Map, which is thought to date to the 13th or 14th centuries, making it the oldest surviving map of the British Isles. The oval landmasses look to be a few miles offshore of Wales, with the southern encompassing an area of seven square miles and the northern at about twice that size, though Haslett and Willis caution that it is hard to make accurate estimates based on the source material.


The Roman cartographer Ptolemy, who lived about 2,000 years ago, appears to place this stretch of Welsh coastline about eight miles further into the sea than it currently stands, suggesting that significant coastal erosion might have occurred over the subsequent centuries. 

To build on that possibility, Haslett and Willis assessed the effects of glaciation over the area during the last ice age. As these icy structures receded during the past 10,000 years, they left a low-lying landscape of soft sediments and deposits in their wake, which have been carved up by geological forces such as rivers. 

Interestingly, the position of the enigmatic islands in the Gough Map line up with underwater “sarns,” which are piles of boulders and gravels shaped by these forces. This hints at the islands’ possible origin story, as well as their watery demise in the face of rising sea levels or, perhaps, a catastrophic flooding event like a tsunami or a storm surge.

“Bathymetrically, the two islands depicted on the Gough Map appear to be located approximately coincident with Sarn Cynfelin, between the Ystwyth and Dyfi estuaries, and Sarn y Bwch, between the Dyfi and Mawddach estuaries, suggesting that the coarse clasts of these sarns may have ‘anchored’ the islands,” the team researchers in the study.

“It appears that the erosion of the two islands was completed by the mid-16th century, as the islands do not appear on later maps, such as Thomas Butler’s Mape off Ynglonnd dated to 1547–1554,” they added.


In a fascinating section of the study entitled “Geomythology,” the researchers share a range of tales and histories that may support these changes to the Welsh coastline, though they said that “caution must be exercised where the boundary between history, literature, and tradition may have become blurred.”

“The tale of Cantre’r Gwaelod might suggest that the lowland, or at least part of it, continued to be inhabited up until the 5th–6th centuries,” the researchers noted. “A number of authors have considered the legend of Cantre’r Gwaelod to represent a folk memory of gradual landscape submergence through rising sea levels” in the millennia since the last ice age.

“In Wales, the Mabinogi description of Bendigeidfran’s crossing to ireland, with only two navigable rivers lying in between, aligns well with the second of these tradition types involving gradual sea-level rise, but the sudden inundation of Cantre’r Gwaelod does not align with a sea-level rise explanation for its demise and instead evokes a more rapid event or series of events,” they added, citing ancient stories of sudden floods in the area.

Taken together, the findings offer a tantalizing explanation for the curious islands depicted in the Gough Map, which may well be evidence for this long-storied Welsh Atlantis—and may, perhaps, serve as a lead to search for other submerged landmasses.

“Of particular geomythological interest are legends regarding now ‘lost’ coastal lowland landscapes, not only in Cardigan Bay but also associated with Cornwall, Brittany, and elsewhere,” the team said.