Lost City of Helike

In the late 2nd century AD, the Greek writer Pausanias wrote an account of how (4-500 years earlier?) in one night a powerful earthquake destroyed the great city of Helike, with a Tsunami washing away what remained of the once-flourishing metropolis.
The city, capital of the Achaean League, was a worship centre devoted to the ancient god Poseidon, god of the sea. There was no trace of the legendary society mentioned outside of the ancient Greek writings until 1861, when an archeologist found some loot thought to have come from Helike - a bronze coin with the unmistakable head of Poseidon.
In 2001, a pair of archeologists managed to locate the ruins of Helike beneath the mud and gravel of the coast, and are currently trying to peice together the rise and sudden fall of what has been called the “real” Atlantis.