abstract:Cius (; Kios), later renamed Prusias on the Sea (; ) after king Prusias I of Bithynia, was an ancient Greek city bordering the Propontis (now known as the Sea of Marmara), in Bithynia (in modern northwestern Turkey), and had a long history, being mentioned by Aristotle, Strabo and Apollonius Rhodius. It was colonized by the Milesians and became a place of much commercial importance.