The Caspian Sea is not usually associated with the story of Atlantis, but as early as the 19th century Moreau de Jonnès proposed the Sea of Azov as the location of Atlantis and that the Black, Caspian and Aral Seas were just remnants of a large ocean.
While this may sound like a wild idea, one modern researcher, Ronnie Gallagher, has written an important paper(b) supporting the concept (see fig.8). This enlarged inland sea is also thought to have extended as far north as the Arctic.
Fessenden cites Strabo (Book 11:7;43), who recounts a tradition that the Caspian had been connected with the Black Sea by way of the Sea of Azov.
Modern proponents of Atlantis in the Sea of Azov have suggested(a) that at the end of the last Ice Age floods of meltwater poured into the Caspian Sea, which in turn escaped through the Manych-Kerch Gateway(c) into what is now the Sea of Azov, but at that time contained the Plain of Atlantis!
Immediately to the south of the Caspian are the Caucasus Mountains which have also had links with Atlantis proposed.