Ys, also spelled Is or Kêr-Is in Breton, and Ville d'Ys in French, is a mythical city on the coast of Brittany that was swallowed up by the ocean. Most versions of the legend place the city in the Baie de Douarnenez.
Flight of King Gradlon, by E. V. Luminais, 1884 (Musée des Beaux-Arts, Quimper)
Lyrics and sheet music for the Breton gwerz "Ar Roue Gralon ha Kear Is" ("King Gradlon and the City of Ys", 1850). This uses the archaic spelling Kear Is for the city of Ys.
Stained glass window by Gabriel Léglise representing "Saint Guénolé, abbé de Landévennec, sauvant le roi Gradlon lors de la submersion de la ville d'Ys" Church of Saint-Germain Kerlaz.
Title page of the first edition of La Vie des saincts de la Bretaigne armorique by Albert Le Grand, 1636
Caer is a placename element in Welsh meaning "stronghold", "fortress", or "citadel", roughly equivalent to an Old English suffix (-ceaster) now variously written as -caster, -cester, and -chester.
The north gate of Cardiff Castle, following the old Roman fortifications and rebuilt along Roman lines.
Caernarfon derives its name from the Edwardian Caernarfon Castle
The Roman fort now known as Segontium derived its name from a latinization of the British community along the Afon Seiont
Carriden House, a refurbished Roman fort which formerly formed part of the Antonine Wall in Scotland.