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Ys (also spelled Is or Kêr-Is in Breton, and Ville d’Ys in French) is a legendary sunken city from Breton folklore, often said to lie in the Baie de Douarnenez off the coast of Brittany, France. It is portrayed as a wealthy, advanced city built on land reclaimed from the sea, famous for its commerce, arts, and luxury—sometimes compared to Atlantis.
The Legend
The story developed between the late 15th and 17th centuries, drawing from older oral traditions and possibly influenced by the Welsh legend of Cantre’r Gwaelod (a sunken kingdom).
Key elements include:
- King Gradlon (or Gralon): A pious ruler who held the key to the dikes protecting the city.
- Princess Dahut (or Ahez): Gradlon’s wayward daughter, often depicted as frivolous, sinful, or a sorceress. In many versions, she steals the key (sometimes with a lover’s encouragement or devilish influence) to open the dikes—either for a party or by mistake—causing the sea to flood and destroy Ys.
- The Flood: Only Gradlon escapes on horseback, often aided by a saint (St. Gwénnolé or St. Corentin). A heavenly voice urges him to throw “the demon” (Dahut) into the sea to survive; she falls or is thrown off and transforms into a mermaid (or morgen) who haunts the waters, combing her hair and singing.
- In some variants, Gradlon himself bears blame for the city’s excesses, or magical elements like korrigans and sea dragons appear.
After the flood, Gradlon flees to Quimper, which becomes his new capital. Folk beliefs claim the city’s bells can still be heard or its ruins glimpsed at low tide.
Etymology and Possible Real Basis
The name Kêr Ys means “low city” in Breton (kêr = city/fort, like Welsh caer; ys/is = low). Some researchers link the myth to real coastal changes: in 2025, marine scientists found submerged ruins near Sein Island, possibly a settlement lost to rising sea levels or erosion over centuries. The legend may reflect memories of ancient flooding events.
Variants of the tale appear in mystery plays, saints’ lives, and folk songs (gwerz). A common Breton saying predicts Ys will rise again when Paris is swallowed by the sea.
