Chalcedon
The site of Chalcedon is located on a small peninsula on the north coast of the Sea of Marmara, near the mouth of the Bosphorus. A stream, called the Chalcis or Chalcedon in antiquity and now known as the Kurbağalıdere (Turkish: "stream with frogs"), flows into Fenerbahçe bay. There Greek colonists from Megara in Attica founded the settlement of Chalcedon in 685 BC, some seventeen years before Byzantium.
Metropolis of Chalcedon
In 451, the year that the local Ecumenical Council took place, the bishopric of Chalcedon was promoted to a metropolis. It was the third oldest metropolis in the region of Bythinia, in northwestern Asia Minor, after Nicaea and Nicomedia, while its prelate officially styled as "Exarch of all Bithynia".