The exclusive hypothesis outlined in the book offers a look at the causes of the death of the "ideal state of Atlanteans" in a new, unexpected way! The author of the book did not look for the sunken island at the bottom of the sea - the author decided to first find the founder of the legendary Utopia - Poseidon! Which of the historical characters was hiding behind this mythical name? With what "Athenians" did Poseidon's subjects wage war? When, in what century, Poseidon's brother Zeus decided to "punish" the offspring of a relative and for what exactly? The author analyzed the information about Atlantis reported by the philosopher Plato, turned to the results of the concept of a new chronology, re-examined mythographic sources, the history of the utopian novel, Shakespeare's "ancient Greek" tragedies. Based on the data obtained, the biography of Poseidon, the great historical character of the great war, was reconstructed. Is the mystery of Atlantis solved?