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 Christianity
Those present at the Council of Chalcedon accepted Trinitarianism and the concept of hypostatic union, and rejected Arianism, Modalism, and Ebionism as heresies (which had also been rejected at the First Council of Nicaea in AD 325). Those present at the council also rejected the Christological doctrines of the Nestorians, Eutychians, and monophysites (these doctrines had also been rejected at the First Council of Ephesus in 431).