Charax in Bithynia was a Byzantine town in what is modern Turkey.
It is 25 kilometres from the former Byzantine Capital Nicomedia, between Nicomedia (Turkish: İzmit) and Helenopolis (Turkish: Hersek) in Bithynia, Asia Minor. It is located on the southern side of the Gulf of Astacus (Turkish: İzmit Körfezi) and is a possible site for the death of Constantine the great.
References
Charax, Bithynia Wikipedia(Text) CC BY-SA