Atlantis was a small continent (about the size of present-day Australia), located in the Atlantic Ocean between North America and Europe, which sank beneath the sea approximately 20,000 years ago. The continent of Atlantis boasted one of the most highly advanced civilizations of its age. Founded in about 19,000 BC, Atlantis predates that of any other known human civilization, and began a mere 4,000 years after the retreat of the last ice age.