Exploration Mysteries: Lyonesse

“And ever pushed Sir Mordred, league by league, back to the sunset bound of Lyonesse, a land of old upheaven from the abyss…” wrote the poet Lord Tennyson. Off the coast of Cornwall, this great kingdom of Lyonesse was swallowed whole by the Atlantic Ocean in one night. A mythical land that rivaled Camelot in Arthurian legend, Lyonesse has engulfed the minds of archaeologists.  


Lyonesse, also called the “City of Lions,” was a prosperous kingdom with beautiful architecture and good-looking people. Flanked by fertile hills, the city contained hundreds of churches and a main cathedral that looked more like a castle than a place of worship. Archaeologists determined that Lyonesse was built on top of the Seven Stones Reef and is located between an area called Land’s End and the Isles of Scilly. 

arthurian legend

Tristan and Isolde. Photo: Edmund Leighton, 1902


Lyonesse was home to an Arthurian knight named Tristan (or Tristram). He was its prince but never had the opportunity to ascend the throne. He was caught up in the business of his uncle, King Mark of Cornwall. Then he found himself in love with King Mark’s wife Isolde, creating one of the most tragic love triangles in Arthurian lore. 

Legend says one night, a man named Trevelyan was out on his white horse when he suddenly heard a loud noise. When he and his horse went to higher ground to investigate, he saw a tidal wave consuming Lyonesse and its people.

This one supposed survivor is said to be the originator of famous Cornish lineages, including the Vyvyan and Trevelyan families. They both bear crests with a white horse, paying homage to their ancestor’s lucky escape from Lyonesse’s destruction. This event allegedly occurred on Nov. 1, 1099. 


Land’s End in Cornwall. Photo: Ollie Taylor/Shutterstock


According to local superstition, people today occasionally hear the bells of Lyonesse’s churches or see forests reemerging. The Lyonesse Project began after the discovery of a sunken forest in 2009. Excavations found submerged stone walls, and some local fishermen discovered artifacts like glass and eating utensils.

Origins of the myth

The myth of sunken cities, prosperous yet decadent and struck by a vengeful higher power, is a recurring theme in many cultures, including throughout the British Isles. In this case, the citizens of Lyonesse committed grievous but unspecified sins, and God punished them by sending a tidal wave.

Archaeologists and geographers Trevor Bell, Aidan O’Sullivan, and Rory Quinn wrote in Discovering Ancient Landscapes Under the Sea that medieval legends possess “ideological intentions.” This refers to stories created to teach listeners valuable moral lessons, like an Aesop’s fable. 

In a further article entitled Lyonesse: The Evolution of a Fable, archaeologist David Bivar posits an origin for the myth. He traces it back to a legend about Charlemagne, who was attempting to crush pagan forces in a town. Charlemagne prayed for God’s wrath to descend upon his foes, and a devastating storm indeed wiped out the town and its citizens. According to Bivar, Charlemagne did, in fact, lay siege to a town run by Saracens. He suggests that these fantastical stories could have come to France from other parts of Europe. 

What’s with the name?

According to some, the name Lyonesse is not just a semi-literal translation of the City of Lions. Rather, the French name may come from Lothian, a Latin place name. Lothian refers to the area outside of Edinburgh, Scotland. This is, however, a bit of a stretch, as it is nowhere near Cornwall. Scotland is not as attached to Arthurian myth as Cornwall and Southern England are. 

Records do show that historians in the Elizabethan era spoke of a city in Cornwall called Lethowstow. It had the same characteristics as Lyonesse and was destroyed by a tidal wave. 

The search

A proposed location for Lyonesse is St Michael’s Mount in Mount’s Bay, Cornwall. On this tidal island, an 8th-century monastery perches on a conical mount of grey rock.  Eons ago, the island was well-forested.

mount st Michael

St Michael’s Mount in Penzance, Cornwall. Photo: Valerie2000/Shutterstock


From 2009-2013, the Lyonesse Project investigated what the Isles of Scilly were like during the Holocene Epoch. It aimed to determine how the physical geography of the Isles of Scilly developed. It also sought to find links to the legend or to discard at least some of the stories.

As it happens, almost 10,000 years ago, the Isles of Scilly were not separate islands but one rather large one. Data shows that the rise in sea level caused over two-thirds of the land from Land’s End to the Isles of Scilly to succumb to the sea.

It is mostly accepted that the ocean completely changed after the last ice age. Twenty thousand years ago, during the Holocene Epoch, a steady rise in temperature and therefore sea levels occurred. Scientists also agree that a mega-tsunami event caused by an underwater landslide also occurred at this time (see Exploration Mysteries: Doggerland). This tsunami would have submerged various lands bordering the Atlantic. 


The Isles of Scilly have always been vulnerable to the ebb and flow of the Atlantic. They are prone to erosion, contain hundreds of tiny rocky islets barely above sea level, and are perpetually at the mercy of the tides. So the Isles have constantly changed for the last few thousand years.

The Lyonesse Project’s main goal was to highlight the dangers that the Isles of Scilly currently face. If climatic change triggered the original disaster that wiped out the whole city, that is also a caution for contemporary society.

The dramatic shift in northwestern Europe’s geography, along with the harsh climatic changes and natural disasters during the Holocene, left a deep scar on the minds of people who lived through it. Like what happened to Doggerland, which happens to be part of the same area, tales of misfortune lived on for generations. The evidence so far suggests that a prosperous community did disappear due to a rise in sea level. This led to oral traditions passed down through families, while contemporary authors picked up the story for their literary masterpieces. 

Kristine De Abreu

Kristine De Abreu is a writer at ExplorersWeb.

Kristine has been writing about Science, Mysteries and History for 4+ years. Prior to that, Kristine studied at the University of Leicester in the UK.

Based in Port-of-Spain, Kristine is also a literature teacher, avid reader, hiker, occasional photographer, an animal lover and shameless ramen addict.