Apparently the earliest records of Atlantis are in the dialogues of Plato 'Timaeus' and 'Critias'.

The story of Atlantis was told to Plato by Critias, who received it from his grandfather Critias, who learned it from his father Dropides, who learned it from Solon.

Solon was a traveler, who in the city of Sais in Egypt learned of the ancient Athenians' victory in the war between Athens, the city of Athena, and Atlantis, the city of Poseidon, nine thousand years before their time. Atlantis was described as an island "in front of" the Pillars of Hercules larger than Libya and Asia put together.

A little mytho-history:

Poseidon gave birth to ten children (five sets of twins) by Cleito. He divided the island into ten parts and divided it among the children. The first-born child, named Atlas, was the first king of Atlantis, prince of the best and largest portion, and both the ocean and the island were named after him. The others were Eumelus/Gadeirus, Ampheres and Evaemon, Mneseus and Autochthon, Elasippus and Mestor, Azaes and Diaprepes, and they were princes of the other nine portions.

Atlantis grew to be an amazingly rich city with, among other things, orichalcum deposits (orichalcum said to be second only in value to gold in those days) and elephants.

Atlantis sank into the sea after one day of violent earthquakes and floods, leaving a large shoal of mud that left the ocean unnavigable.

The names in the story are unabashedly Hellenic: Critias says this is because the Egyptian story had translated the names into that language, and Solon was able to retranslate them into Greek. (Sure.)

And that's all I know about that.