Mysia was an ancient region in northwest Anatolia. It was part of the province of Asia in the Classical Roman era. In Late Antiquity, it was reorganized as the Diocese of Asia, with the province of Hellespont comprising much of what was Mysia (along with the Troas). Its capital was Kyzikos. Abydos, a city on the Hellespont, was one of two customs houses for shipping to Constantinople. While the civil province disappeared in the 7th century, the ecclesiastical diocese survived with Kyzikos as the metropolis. The region was incorporated into the Opsikion theme. The region was largely conquered by the Karesi Principality in the early 14th century and later by the Ottomans in the 1330s. Mysia was centered modern Balıkesir Province and included parts of Çanakkale and Bursa provinces.