Constantinople
Constantinople (; ) was the capital city of the Roman/Byzantine Empire (330–1204 and 1261–1453), and also of the brief Crusader state known as the Latin Empire (1204–1261), until finally falling to the Ottoman Empire (1453–1923). It was reinaugurated in 324 from ancient Byzantium as the new capital of the Roman Empire by Emperor Constantine the Great, after whom it was named, and dedicated on 11 May 330. The city was located in what is now the European side and the core of modern Istanbul.
Western Roman Empire
Constantius II focused most of his power in the East. Under his rule, the city of Byzantium – only recently re-founded as Constantinople – was fully developed as a capital. At Constantinople, the political, economic and military control of the Eastern Empire's resources would remain safe for centuries to come. The city was well fortified and located at the crossroads of several major trade and military routes. The site had been acknowledged for its strategic importance already by emperors Septimius Severus and Caracalla, more than a century prior.