Atlantis could have existed but no one knows for sure.
There are many suggestions and places that people think it is.
. . . But there is one place with a volcano in the center that could have gone KABOOM! And wipe out the entire island. . . Gone forever!
The concept of Atlantis is generally agreed to have originated with Plato as a foil to Athens. There is no substantial evidence supporting that it ever physically existed. Yes one could come up with scenarios in which it might have existed and hidden from humanity, but without real-world evidence these are speculations I'm not willing to put my faith in.