The Roman Empire in the East continued to exist until 1453 with its capital city being Constantinople – now known as Istanbul.
Constantinople fell to the Turks who established the Ottoman Empire in its place which survived until 1923 when the Sultanate was abolished and the Republic of Turkey created.
Arteifacts of both the Roman and Ottoman empires remain to this day in Istanbul with probably the most significant being the Hagia Sofia – originally a Church but converted to a Mosque under the Islamic ottomans and then a museum under the republic.