The civilization of the Empire of Atlantis actually existed 11,500 years ago, when it was destroyed in a war with the Lemurian Empire of Mu. At that time, it was located on the surface of the Gobi Desert, with two underground cities, Agartha Alpha and Beta, connected by a tunnel, each underground, in the Gobi Desert and in the Himalayas, where descendants of extraterrestrial origin still exist today, with advanced space travel technology. https://www.futureofmankind.co.uk/Billy_Meier/Atlantis
Summary: Followed by contact 9 on March 21, 1975. Again with Semjase, who explains that "the descendants of those who had settled on distant worlds have returned (contact 70 explains from Beta Centauri). They were again under the leadership of an IHWH (described in contact 70 as Jschwjsch Atlant, married to Jschrisch Karyatide. It is explained in contact 60, as well as later in this contact 9, that another Jschwjsch called Arus "the Barbarian" attempted to conquer Atlantis and succeeded in conquering Hyperborea, the area that is now Florida), under whose command they built on Atlantis and Mu. They built huge cities on each of the two separate continents (described in contact 55 as
North/South America and Europe/Africa). For thousands of years they lived in friendship and peace, until a few scientists were again overcome by the old thirst for power and might and tried to seize the government. But, fed up with wars, the nations rose up against them, and they occupied spaceships and fled into outer space; this being about 15,000 years ago in Earth's chronology." https://www.futureofmankind.co.uk/Billy_Meier/Atlantis
In contact 55 of June 14, 1976, Semjase gives Billy the explanation that the Great Atlantis was located between the separate continents of North/South America and Europe/Africa, placing it roughly in the current equatorial climate zone. Little Atlantis being in the Santorini region, which partly constitutes the Greek archipelago in website the Mediterranean, Aegean and Crete Seas. It is again briefly explained that the Great Atlantis was damaged and subsequently sank into the ocean as a result of war activities with the inhabitants of Mu, which at that time was a country on the site of the current Chinese Gobi Desert. But the country of Mu was also destroyed during these war activities and ceased to exist. However, the underground city of Agartha remained due to its underground construction. https://www.futureofmankind.co.uk/Billy_Meier/Atlantis
Destruction The destruction of Little Atlantis occurred approximately 6,000 years after these war activities, as reported in Contact 55. This suggests its survival after the tsunami destruction of Greater Atlantis. Its geographical location allowed it to survive despite its coastal position, causing theoretical damage. Research into this region and its history seems to indicate the existence of the city of Pavlopetri[1], which lies underwater off the coast of southern Laconia in the Peloponnese, Greece. It is approximately 5,000 years old, placing its construction age at approximately 6,500 years after the destruction of Greater Atlantis, only 500 years after the destruction of Little Atlantis, as described by Semjase in this contact.
In Contact 60 dated July 8, 1976, Semjase gives Billy a detailed explanation of the history leading up to and including the war that led to the total destruction