Constantinople (Roman name: Constantinopolis; Greek: Κονσταντινουπολις) is an old name of the present city of Istanbul in Turkey. Its original name was Byzantium (Greek Byzantion).
"Constantinople" is an Anglicization of "Κονσταντινουπολις," which means "City of Constantine" in Greek, and was given that name in reference to the Roman emperor Constantine I when he made it the capital of the Roman Empire on May 11, 330 A.D. Constantine actually named it "Nova Roma", but that name never came into common use. Rome retained its political and commercial privileges.
Constantinople was the capital of the Eastern Roman Empire. It was sacked by the Fourth Crusade in 1204 and then re-captured by Nicaean forces under the command of Michael VIII Palaeologus in 1261.
Constantinople and the Byzantine Empire finally fell to the Ottoman Empire on May 29, 1453. See the Fall of Constantinople. When the Republic of Turkey was founded in 1923, the capital moved from Istanbul to Ankara. Ottoman people were calling their capital city by various names, including Constantinople. Istanbul became the official name as late as 1930.
See also: Golden Horn, Hagia Sophia, Hippodrome of Constantinople, the Bosporus