Or one of the other 10000+ highly advanced super civilisations filled with picture perfect uber humans that existed XX-thousands of years ago and travelled all over the globe, star system and other dimensions of which people like to dream about on the internet.
One needn't have to believe the comic book version in order to think it likely that there was relatively advanced civilization in many parts of the world, and that it might reach back much farther than previously advertised.
The idea of Atlantis being a well civilized region, even one of many such places lost to history (so far) isn't really all that much of a stretch.