This work suggests a solution to a mystery which has baffled scholars for nearly 2400 years - since Plato first wrote about Atlantis. It reviews previous theories and shows why they will not work. Atlantis could not have been in the Atlantic; nor was it the volcanic island of Santorini near Crete, as currently held. Through an analysis of the sources available to Plato, it becomes clear that the story of Atlantis came from western Turkey, where about 3400 years ago, a major Bronze Age city was devastated by an earthquake and submerged beneath a lake. The new theory also provides an explanation of how and why this event grew into the story of a lost continent.