Ask A Historian

[Minimalist]

Is there any evidence for Atlantis?

Well there are fictional accounts in two of Plato's dialogues: Timaeus and Critias. 

But as far as what served as his inspiration, I submit this as the most likely culprit.

http://www.bbc.co.uk/science/horizon/2001/helike.shtml

On a winter night in 373 BC, the classical Greek city of Helike was destroyed by a massive earthquake and tidal wave. The entire city and all its inhabitants were lost beneath the sea. What has bewitched archaeologists about Helike is that it was engulfed just when ancient Greece was reaching its height; when the philosophy and art that inspired the western world for thousands of years were invented.

In 373 Plato was 55 years old and living in Athens roughly 100 miles from Helike which was near the mouth of the Corinthian Gulf.  Timaeus written some 10-15 years after the destruction of Helike (and Critias is also a late dialogue) could easily have their tales of a city wiped out by the gods inspired by an actual event which happened during Plato's lifetime.