Tackling the whole of civilization along the Volga is too big a project for the moment. My idea for Volgastan is based on a PoD where Greek settlers go further up the Don and cross over to the Volga. In the Volgan Delta, a Greco-Scytherian civilization develops. What would the cities be called?
What I want to do is explore this civilization as its conquered by nomads some time after the fall of Rome. More than enough Nomads to storm the place. First, the Huns. They would be enough to drive anybody on to islands.