On the subject of cities, I think it may be necessary to add a city between Constantinople and the rest of the world, as it seems that the mightiest fortress between China and Japan (spanning the rest of the globe ) falls a little too much. Furthermore the Visigoths historically lingered for a while in nowadays Bulgary; rendered impossible without another city in that space. Adrianople, being one of the bigger cities of the ERE, seems to me as a good candidate, don't you agree?