Overview
Bithynia was an ancient region, kingdom and Roman province in the northwest of Asia Minor (present-day Turkey), adjoining the Sea of Marmara, the Bosporus, and the Black Sea. It bordered Mysia to the southwest, Paphlagonia to the northeast along the Pontic coast, and Phrygia to the southeast towards the interior of Asia Minor.
Hellenistic Bithynia was an independent kingdom from the 4th century BC. Its capital Nicomedia was rebuilt on the site of ancient Astacus in 264 BC by Nicomedes I of Bithynia. Bithynia was bequeathed to the Roman Republic in 74 BC, and became united with the Pontus region as the province of Bithynia et Pontus. In the 7th century it was incorporated into the Byzantine Opsikion theme.
It became a border region to the Seljuk Empire in the 13th century, and was eventually conquered by the Ottoman Turks between 1325 and 1333.
Description
Several major cities sat on the fertile shores of the Propontis (which is now known as Sea of Marmara): Nicomedia, Chalcedon, Cius and Apamea. Bithynia also contained Nicaea, noted for being the birthplace of the Nicene Creed.
According to Strabo, Bithynia was bounded on the east by the river Sangarius (modern Sakarya river), but the more commonly received division extended it to the Parthenius, which separated it from Paphlagonia, thus comprising the district inhabited by the Mariandyni. On the west and southwest it was separated from Mysia by the river Rhyndacus and on the south it adjoined Phrygia and Galatia.
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