Building a city below sea level is a great way to ensure it winds up a legend at some point during its lifetime. The city of Ys, built below sea level by the King of Cornouaille, Gradlon, is one such city, once a home to many and now a legend of French folklore. Legend has it that the city was built for the Kings daughter, Dahut, who loved the sea. Which was probably the first problem they made.. we’re just kidding ladies. It is said that the failsafe to keep the city from flooding, a large gate, was opened during a violent storm, allowing a tall wave to collapse on the city and engulf it completely. Some versions state that Gradlon’s daughter, Dahut, for whom he built the city, was tricked by the Devil to open the gate. Others claim a drunken Dahut was responsible for the city’s collapse. The city remains a mystery today, though some think it may actually be at the base of the Douarnenez Bay.