This post has little to do with fantasy literature, per se. At least not directly. The connection is that the story of Atlantis is kind of fantastical.
The story of Atlantis comes to us from Plato, specifically from his dialogue The Timaeus. I never studied that one in college. I’ve read bits and pieces of it—mostly the stuff about the demi-urge and such. Anyway, within the dialogue we are given the legend of Atlantis in which Plato tells of an ancient advanced civilization that was wiped out in a cataclysm of some sort—earthquakes and floods, basically—which not only destroyed the Atlantean civilization in its entirety, but devastated the Athenian nation as well. Plato provides a number of details about the Atlantean civilization which I will not go into here. I will say, having read several books on the subject now, that I believe the Atlantean Legend is based on a real nation-state that once existed. Exactly where it was, though, I have no idea. It could have been somewhere in the Mediterranean, somewhere along the North African coast, somewhere along the Spanish coast, somewhere in the middle of the Atlantic, or even in Antartica.
However, I would like to distinguish here between Plato’s Atlantis and the New Age Atlantis. Plato’s Atlantis is the Atlantis of which he wrote. It may have been a technologically advanced nation, but only a technologically advanced nation relative to its time. Perhaps Plato’s Atlanteans mapped South and North America; perhaps they knew of Antartica; but they did NOT fly around in planes, nor did they develop a space program based on crystals or something like that. Why do I say this? Because according to the Platonic Legend, the Atlanteans were at war with the Athenians, and the Athenians won said war. If the Atlanteans were so advanced they were flying around in planes, they would have mopped the floor with the primitive Athenians. And they didn’t. They lost. No super-technology for you.
The New Age Atlantis is the term I would use to refer to some ancient culture that may have existed in ages past with technology on par with or perhaps even exceeding our own. Plato’s Atlantis provides no support to such a theory. Such an Atlantis may have existed, but we must look elsewhere for evidence (we only refer to it as Atlantis for romantic reasons for surely it was called something else during its times). Things like the Nazca lines in South America, or those tiny golden airplanes that were found, again in South America. A New Age Atlantis would require a global catastrophe to wipe out and reset the humans of this planet back to the beginnings of the Stone Age. Such an event is possible but, at first blush, appears kind of loony. That said, perhaps I’ve watched one too many episodes of Ancient Aliens, because I’ve grown convinced that there was either a New Age Atlantis-like civilization in our past or we actually were being visited by aliens as far back as our prehistory. The evidence presented on Ancient Aliens is (sometimes) quite compelling.