The Critias dialog
The dialog Critias mentions the same participants and in fact this story is the continuation of the previous one. This dialog is fully dedicated to the story about Athens and Atlantis.
At that time Athens was the centre of the big and unusually fertile lands. It was inhabited by the good people that lived in the country with the ideal state structure. Plato gives the contrast of good and great Athens and the Atlantis that was the warriors.
According to Plato the father of Atlantis was Poseidon that fell in love with the mortal girl. She gave birth to ten sons with the oldest Atlas. Poseidon gave the island to these sons and made them the fathers of the royal families. The centre of the island was the hill that was situated in 8-9 kilometres from the sea.
To protect the city Poseidon surrounded it by three maritime and two land protections. The Atlases built the bridges and made the channels across these protections connecting it with the main centre that was the central island.
The island had numerous temples that were decorated with the gold and silver as well as with the golden statues. The stone of the black, red and white colours were got from the land in the centre of the island.
Some constructions of these stones were made simple and didn't attract attention other constructions were made coloured for fun.
Plato pays much attention to the description of the great richness and the fertility of the island. It was highly-populated and had the rich natural world.