Ys, a magnificent city said to have once stood on the coast of Brittany before being swallowed by the sea. Built by King Gradlon for his daughter Dahut, Ys was protected by massive dikes and gates, but the city fell when Dahut—whether through folly, temptation, or betrayal—opened the sea barriers. A storm surged in, drowning the city and leaving only echoes beneath the waves. While Ys is most likely a myth rooted in cultural memories of coastal floods, its story has endured for centuries as a symbol of hubris, divine retribution, and humanity’s fragile relationship with the sea.