Byzantium

nouns

an ancient city on the Bosporus founded by the Greeks; site of modern Istanbul; in 330 Constantine I rebuilt the city and called it Constantinople and made it his capital
is a part of
a continuation of the Roman Empire in the Middle East after its division in 395
is an instance of (narrower)
a large and densely populated urban area; may include several independent administrative districts
"Ancient Troy was a great city"
a continuation of the Roman Empire in the Middle East after its division in 395