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.
Catholic theology
The Chalcedonian Creed, developed at the Council of Chalcedon in 451,
though not accepted by the Oriental Orthodox Churches, taught Christ "to be acknowledged in two natures, inconfusedly, unchangeably, indivisibly, inseparably": one divine and one human, and that both natures are perfect but are nevertheless perfectly united into one person.