Arcadia
Arcadia is a central region of the Peloponnese in Greece. It is one of a number of locations that have been proposed as inspiring elements of Plato’s Atlantis story. One proponent is Oliver D. Smith who argues that “Plato based his king Atlas on a mythical Arcadian king of the same name and his main inspiration for Atlantis was the town Methydrium and nearby city Megalopolis, both in Arcadia.”
This, together with some other details, such as similarities between the ten kings of Atlantis and the ten kings of Arcadia led Smith to his conclusion(a).