There is no mention that Plato placed Atlantis beyond the Pillars of Hercules, which are usually identified with the Strait of Gibraltar, i.e. in the Atlantic Ocean.
Atlantis is probably mythical, but it isn't the only mythical Atlantic island to go missing. There's also Brasil (or Hy Brasil), an island once regularly shown on maps off the coast of Ireland:
I mean Brasil is fairly recent, go back far enough and there's a land bridge between Europe mainland and the modern day British isles (Doggerland, https://en.wikipedia.org/wiki/Doggerland)
Atlantis is probably mythical, but it isn't the only mythical Atlantic island to go missing. There's also Brasil (or Hy Brasil), an island once regularly shown on maps off the coast of Ireland:
https://en.wikipedia.org/wiki/Brasil_(mythical_island) https://www.irishcentral.com/roots/history/hy-brasil-ireland...