Also City of Is; in Breton Kêr Is, Kêr-Is, Kêr Iz, Kêr-Iz, Ker Is. How the legendary city of Ys came to be submerged under the Bay of Douarnenez in south-west Brittany is explained in the best-known narrative from Breton tradition. At least three versions survive; each portrays at least three characters: Gradlon (or Gralon) Meur [the great], a pious, saintly king who has protected his city by building a protective dike; Dahut (also Dahud, Ahè, Ahès), his wilful and wayward daughter; and the abbé Guénolé, founder of the first monastery in Brittany at Landévennec. In the oldest version Dahut secretly entertains her lover, and the two of them, excited by wine, steal Gradlon's key to open the dike, flooding the city.
The more familiar second version depicts Ys as a commercial centre so given to luxury as to arouse the ire of Guénolé, who, like the biblical Jeremiah, foretells ruin. Among the wickedest of Ys's citizens is Dahut, who has made a crown of her vices and has taken as pages the seven deadly sins. A small boy named Kristof, whose encounter with a magical fish has provoked Dahut's scorn and thus caused her to be pregnant, removes the enchanted oak tree protecting the city. One night at a feast a devilish stranger whispers his love into Dahut's ear and bids her take the key to the dike from around her sleeping father's neck. As soon as the key is put in the dike the sea begins to rush in, but Guénolé wakes Gradlon and urges him to flee. The king charitably takes his daughter with him on the steed Morvarc'h [horse of the sea] until he hears a voice crying out to cast aside his demon passenger or he also will be lost. With his heart breaking, Gradlon complies and the waters immediately recede, allowing him to reach Quimper safely. Dahut becomes a siren-like mermaid, calling out to sailors about to be wrecked, but Ys is submerged either at Douarnenez or under the Étang de Laval.
In the third version, from ballad tradition, Gradlon leads the people in extravagance of every kind, and he freely gives the dike's key to Dahut, who misuses it. When the city is flooded Dahut becomes a mermaid who haunts the waters at Douarnenez.
A statue of Gradlon was erected between the two towers of the cathedral in Quimper, damaged in 1793, and restored in 1859. The legend that church bells can still be heard ringing below the waters of the Bay of Douarnenez inspired Claude Debussy's overture La Cathédrale engloutie [The Sunken Cathedral]. In colloquial Breton Ys lends itself to a familiar pun with the modern capital of sin: Par [Bret., like] Is.
See Charles Guyot, The Legend of the City of Ys, trans. Deirdre Cavanagh (Amherst, Mass., 1979);Rachel Bromwich, ‘Cantre'r and Ker-Is’, in Cyril Fox and Bruce Dickens (eds.), The Early Cultures of North-West Europe (Cambridge, 1950), 217–41.