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.
Chalcedonian Definition
The Chalcedonian Definition (also called the Chalcedonian Creed) was adopted at the Council of Chalcedon in AD 451. Chalcedon was an early centre of Christianity located in Asia Minor (modern Turkey). The council was the fourth of the Ecumenical Councils that are accepted by Chalcedonian churches which include the Eastern Orthodox, Catholic, and most Protestant churches. It was the first council not to be recognised by any Oriental Orthodox church; these churches may be classified as non-Chalcedonian.