Plato's Atlantis From the Socratic Dialogues of Timaeus and Critias

According to the Egyptians, or rather what Plato described Critias reporting what his grandfather was told by Solon who heard it from the Egyptians, once upon a time, there was a mighty power based on an island in the Atlantic Ocean. This empire was called Atlantis and it ruled over several other islands and parts of the continents of Africa and Europe.

Atlantis was arranged in concentric rings of alternating water and land. The soil was rich, said Critias, the engineers technically accomplished, the architecture extravagant with baths, harbor installations, and barracks. The central plain outside the city had canals and a magnificent irrigation system. Atlantis had kings and a civil administration, as well as an organized military. Their rituals matched Athens for bull-baiting, sacrifice, and prayer.

But then it waged an unprovoked imperialistic war on the remainder of Asia and Europe. When Atlantis attacked, Athens showed its excellence as the leader of the Greeks, the much smaller city-state the only power to stand against Atlantis. Alone, Athens triumphed over the invading Atlantean forces, defeating the enemy, preventing the free from being enslaved, and freeing those who had been enslaved.

After the battle, there were violent earthquakes and floods, and Atlantis sank into the sea, and all the Athenian warriors were swallowed up by the earth.

https://www.thoughtco.com/platos-atlantis-from-the-timaeus-119667