|Style over substance|
Atlantis is the name given to a mythical island first mentioned by the Greek philosopher Plato in his dialogues Timaeus and Critias.
According to Plato, Atlantis lay beyond the "pillars of Heracles" (generally assumed to be the Rock of Gibraltar), which would presumably place it in the Atlantic Ocean. He claimed that it was an important naval power around 10,000 years ago and that it had attempted to invade Greece.
Sadly, the island suffered some sort of catastrophe and was swallowed by the sea in a single day. Over the years it went from a fictional cautionary tale about hubris to a legendary land of ancient high technology and whizzy powers, and ultimately came to be a beloved meme of the Spiritualism, Theosophy, and eventually the New Age movements.
 Miscellaneous woo
Helena Blavatsky considered Atlantis to be the ancestral homeland of all modern human races. In reality, paleontologists have concluded that humans as a species originated in eastern Africa. Quite a bit of modern woo is said to date from Atlantis: the island would eventually become a common trope in science fiction and fantasy writing, for example as the lost continent of Númenor in the writings of J. R. R. Tolkien, or the setting of the science fiction show Stargate Atlantis.
There are, allegedly, connections between Atlantis, Hitler and Nazism. One relatively reasonable suggestion is that Hitler based his views about the supposedly superior Aryan race on what he imagined the people of Atlantis had been like. This is plausible but the chief proponent of this claim has no evidence except unrevealed confidential sources, so historians cannot assess the claim. A less plausible story is that Hitler escaped to Atlantis after Berlin fell. There was no body and DNA evidence was not yet possible in 1945 so speculation that Hitler might have escaped was reasonable then. But why Atlantis? Hitler was an inhabitant of Atlantis who fell to the dark side.
 Invention and reality
It is not known if Atlantis was a fanciful invention on Plato's part, or if stories about it were based on real events that may have happened in the Mediterranean Sea. Attempts to place it within mainstream history have mostly centered on the Minoan and Mycenean civilizations. One of the main contenders for the title of Atlantis is the island of Thera, which was mostly destroyed in 1628 BCE when the volcano on which it was located erupted (modern Thera, aka Santorini, is a crescent-shaped assembly of three islands surrounding two central, constantly steaming volcanic islands). The eruption of Thera was probably a major factor in the collapse of the Minoan civilisation, so it's not beyond reason that a major Minoan city could have been built on Thera and been destroyed by the eruption. The problem is that Thera is firmly in the Mediterranean, not outside of it, although Plato may have changed the location for the purposes of his story.
Extensive mapping of the seafloor has revealed that there is actually very little continental crust under the oceans, and virtually none of it is in the Atlantic Ocean, apart from continental shelves. So far, the only evidence of Atlantis being an actual continent in the Atlantic is the occasional mapping artifact. Notwithstanding the complete lack of evidence for any large island existing in the Atlantic, there are still those prepared to imagine such a thing as part of a lost prehistoric civilization. Potential candidates for the "real" Atlantis still continue to be put forward and virtually everything to the west of the Straits of Gibraltar (the only concrete description of its location according to Plato) has been suggested. Some have suspected Atlantis to somehow refer to the South American continent, as there are raised plains that can be associated with descriptions in the written legend. Another claim made in 2011 cites the discovery of a sunken city off of the coast of Spain, which does bear some resemblance to Plato's description, such as its location being west of Gibraltar and the city being swamped by a tsunami.
Quite a few superheros claim to be from Atlantis; the most famous among them are Aquaman and Namor. 
 See also
- Gardner, Martin. Fads and Fallacies in the Name of Science, Dover Publications, 1957.
- Garner, James Finn. Apocalypse Wow!, New York: Simon and Schuster, 1997, ISBN 0684836491.