The foundation of Istanbul is usually dated in 667 BC, when the Megarian King Byzas arrived at the mouth of the Bosphorus. The legend goes that Byzas had consulted the oracle at Delphi, Greece, as to where he should found a city and been given the cryptic reply ‘Opposite the blind’.
The king spotted a small settlement called Chalcedon, at what is now Kadıköy, on the Asian shore of the Bosphorus. He presumably thought to himself this spot must have been the Megarian equivalent of ‘They must be blind’, since the settlers had missed the obvious spot, on the hill where the Topkapi Palace now stands. This hill has spectacular views of the Golden Horn, the Bosphorus and the Sea of Marmara. This is where Byzas chose to build his town, which was called Byzantium.
Byza’s rule was short-lived. In 546 BC the Persians arrived and occupied the town under Otonis, who had brought a massive army of 700.000 with the aim of conquering Eastern Europe. He was never successful and in 479 BC the city was once again Greek.
For many years to come, Byzantium was part of the Roman Empire. This lasted until 196 AD, when the city joined a rebellion in a Roman civil war and was punished by Emperor Septimius Severus. Septimius raised the walls, slaughtered most of the inhabitants and later rebuild the city.
Read more about how Byzantium became Constantinople.