Portugal
This theory states that Atlantis was no other than the Chalcolithic civilization of Vila Nova de Sao Pedro and that Mycenean Greeks would have fought against them for the control of tin routes in alliance with neighbour Iberian civilization of El Argar, which shows some clear Hellenization in its B phase. The catastrophe described would be an earthquake with tsunami like the one suffered by Lisbon in 1755.
The recent location of a sea branch reaching Zambujal (the main city of this culture) and the evidence that it was silted somehow when VNSP ended seem to add some weight to this theory.
Source: Wikipedia
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Actually, this is pretty close, but no cigar. Lusitania was the mainland sector of the Atlantean empire (the great plain). But Atlantis proper was a supervolcanic island off Portugal’s coast that exploded and sank in the 17th century BC. (See Roots of Cataclysm, Algora Publ.Ny 2009)