Chalcedon (modern Kadıköy) was a city of Bithynia, located directly across the Bosphorus from Constantinople. Chalcedon was permanently overshadowed by the nearby capital, but it did benefit in the 4th and 5th centuries from the generosity of imperial dignitaries who enlarged its harbor and built palaces and churches in the vicinity. Chalcedon was taken by the Persians in 615 and 626 and by the Arabs during their attacks on Constantinople. It was the main camp for the First, Second, and Fourth Crusades before their further advances. Chalcedon fell to the Ottomans in 1350. The Byzantine remains of Chalcedon have disappeared: they consisted of a palace, a hippodrome, and numerous churches. Most notable was that of St. Euphemia, built outside the walls in the 4th century and seat of the Council of Chalcedon in 451. It contained the circular domed shrine of the saint, from whose tomb was said to issue a miraculous flow of blood, and was decorated with paintings showing scenes from her life. It was destroyed by the Persians. The suburbs of Chalcedon contained the important monastic centers of Rouphinianai and Mt. Auxentios. Originally a suffragan bishopric of Nicomedia, Chalcedon became an independent metropolis in 451.
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Belke, Klaus. Bithynien und Hellespont (TIB 13)
Oxford Dictionary of Byzantium