The Timaeus dialog
The dialog of Plato starts with the thought of Socrates and his friend Timaeus about the best state structure. Describing the ideal government in a few words Socrates show the desire to consider the behaviour of the country during the war with other governments. In response to this desire another participant of the dialogs tells about the war of Athens with Atlantis. According to him the story was heard by him from his father that heard this story from Solon who heard this story being in Egypt. The main plot of the story is the next: about 9000 years ago Athens was the great state being the powerful and helping state. The main enemy of this country was the mentioned Atlantis.
According to this story Atlantis was bigger than Libya and even Asia. This government covered the territory from the Libya to Egypt as well as the whole Europe. All powers of this country were directed to conquer Athens. Athens started to protect its freedom. All their companions betrayed them but the great inhabitants managed to defend their motherland killing the Atlases and bringing the freedom to the conquered peoples. Then the great natural disaster followed in the result of which the whole army of Athens died and Atlantis sank.
But this dialog mentions Atlantis only in a few words while the second dialog gives more detailed information about Atlantis. Nevertheless Atlantis was mentioned.