Timaeus

Timaeus Plato - The dialogue takes place the day after Socrates described his ideal state. In Plato's works such a discussion occurs in the Republic. Socrates feels that his description of the ideal state wasn't sufficient for the purposes of entertainment and that "I would be glad to hear some account of it engaging in transactions with other states" (19b).
Hermocrates wishes to oblige Socrates and mentions that Critias knows just the account (20b) to do so. Critias proceeds to tell the story of Solon's journey to Egypt where he hears the story of Atlantis, and how Athens used to be an ideal state that subsequently waged war against Atlantis (25a). Critias believes that he is getting ahead of himself, and mentions that Timaeus will tell part of the account from the origin of the universe to man.