Atlantis (in Greek, "island of Atlas") is a legendary island first mentioned in Plato's dialogues Timaeus and Critias.
In Plato's account, Atlantis was a naval power lying "in front of the Pillars of Hercules" that conquered many parts of Western Europe and Africa 9,000 years before the time of Solon, or approximately 9600 BC. After a failed attempt to invade Athens, Atlantis sank into the ocean "in a single day and night of misfortune".
For it is related in our records how once upon a time your State stayed the course of a mighty host, which, starting from a distant point in the Atlantic ocean, was insolently advancing to attack the whole of Europe, and Asia to boot. For the ocean there was at that time navigable; for in front of the mouth which you Greeks call, as you say, 'the pillars of Heracles,' there lay an island which was larger than Libya and Asia together; and it was possible for the travelers of that time to cross from it to the other islands, and from the islands to the whole of the continent over against them which encompasses that veritable ocean. For all that we have here, lying within the mouth of which we speak, is evidently a haven having a narrow entrance; but that yonder is a real ocean, and the land surrounding it may most rightly be called, in the fullest and truest sense, a continent. Now in this island of Atlantis there existed a confederation of kings, of great and marvelous power, which held sway over all the island, and over many other islands also and parts of the continent
But at a later time there occurred portentous earthquakes and floods, and one grievous day and night befell them, when the whole body of your warriors was swallowed up by the earth, and the island of Atlantis in like manner was swallowed up by the sea and vanished; wherefore also the ocean at that spot has now become impassable and unsearchable, being blocked up by the shoal mud which the island created as it settled down
The concept of Atlantis attracted Nazi theorists. In 1938, SS Officer Heinrich Himmler organized a German expedition to Tibet in 1939 to search for Aryan Atlanteans, although this suggestion has been criticised as inaccurate and that the expedition was looking for the origins of the 'Europid' race or that it was a more general biological expedition . According to Julius Evola, writing in 1934, the Atlanteans were Hyperboreans—Nordic supermen who originated on the North pole (see Thule). Similarly, Alfred Rosenberg (The Myth of the Twentieth Century, 1930) spoke of a "Nordic-Atlantean" or "Aryan-Nordic" master race.