Constantinople (Greek: Κωνσταντινούπολις, Latin: Constantinopolis, Turkish: Istanbul) was the imperial capital of the Roman Empire, the Byzantine/Eastern Roman Empire, the Latin Empire and the Ottoman Empire. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.
Constantinople as the name of the city was officially dropped in favour of the Turkish name Istanbul in 1930 with the Turkish Postal Service Law, as part of Atatürk's national reforms. This name in turn derives from the Greek and Slavic colloquial name Stambol; see Names of Istanbul for fuller discussion.
Constantinople was founded by the Roman emperor Constantine I on the site of an already existing city, Byzantium, settled in the early days of Greek colonial expansion, probably around 671-662 BC. The site lay astride the land route from Europe to Asia and the seaway from the Black Sea to the Mediterranean, and had in the Golden Horn an excellent and spacious harbour.
Constantine had altogether more colorful plans. Having restored the unity of the Empire, and being in course of major governmental reforms as well as of sponsoring the consolidation of the Christian church, he was well aware that Rome was an unsatisfactory capital. Rome was too far from the frontiers, and hence from the armies and the Imperial courts, and it offered an undesirable playground for disaffected politicians. Yet it had been the capital of the state for over a thousand years, and it might have seemed unthinkable to suggest that the capital be moved to a different location. Nevertheless, he identified the site of Byzantium as the right place: a place where an emperor could sit, readily defended, with easy access to the Danube or the Euphrates frontiers, his court supplied from the rich gardens and sophisticated workshops of Roman Asia, his treasuries filled by the wealthiest provinces of the Empire.
Constantinople was built over six years, and consecrated on 11 May 330. Constantine divided the expanded city, like Rome, into 14 regions, and ornamented it with public works worthy of an imperial metropolis. Yet initially Constantine's new Rome did not have all the dignities of old Rome. It possessed a proconsul, rather than an urban prefect. It had no praetors, tribunes or quaestors. Although it did have senators, they held the title clarus, not clarissimus, like those of Rome. It also lacked the panoply of other administrative offices regulating the food supply, police, statues, temples, sewers, aqueducts or other public works. The new programme of building was carried out in great haste: columns, marbles, doors and tiles were taken wholesale from the temples of the Empire and moved to the new city. Similarly, many of the greatest works of Greek and Roman art were soon to be seen in its squares and streets. The Emperor stimulated private building by promising householders gifts of land from the Imperial estates in Asiana and Pontica, and on 18 May 332 he announced that, as in Rome, free distributions of food would be made to the citizens. At the time the amount is said to have been 80,000 rations a day, doled out from 117 distribution points around the city.
Constantine laid out a new square at the centre of old Byzantium, naming it the Augustaeum. The new senate-house (or Curia) was housed in a basilica on the east side. On the south side of the great square was erected the Great Palace of the emperor with its imposing entrance, the Chalke, and its ceremonial suite known as the Palace of Daphne. Nearby was the vast Hippodrome for chariot-races, seating over 80,000 spectators, and the famed Baths of Zeuxippus. At the western entrance to the Augustaeum was the Milion, a vaulted monument from which distances were measured across the Eastern Roman Empire.
From the Augustaeum led a great street, the Mese (Greek: Μέση [Οδός] lit. "Middle [Street]"), lined with colonnades. As it descended the First Hill of the city and climbed the Second Hill, it passed on the left the Praetorium or law-court. Then it passed through the oval Forum of Constantine where there was a second Senate-house and a high column with a statue of Constantine himself in the guise of Helios, crowned with a halo of seven rays and looking towards the rising sun. From there the Mese passed on and through the Forum of Taurus and then the Forum of Bous, and finally up the Seventh Hill (or Xerolophus) and through to the Golden Gate in the Constantinian Wall. After the construction of the Theodosian Walls in the early 5th century, it would be extended to the new Golden Gate, reaching a total length of seven Roman miles.
The first known Prefect of the City of Constantinople was Honoratus, who took office on 11 December 359 and held it until 361. The emperor Valens built the Palace of Hebdomon on the shore of the Propontis near the Golden Gate, probably for use when reviewing troops. All the emperors up to Zeno and Basiliscus were crowned and acclaimed at the Hebdomon. Theodosius I founded the Church of John the Baptist to house the skull of the saint (today preserved at the Topkapı Palace in Istanbul, Turkey), put up a memorial pillar to himself in the Forum of Taurus, and turned the ruined temple of Aphrodite into a coach house for the Praetorian Prefect; Arcadius built a new forum named after himself on the Mese, near the walls of Constantine.
Gradually the importance of Constantinople increased. After the shock of the Battle of Adrianople in 378, in which the emperor Valens with the flower of the Roman armies was destroyed by the Visigoths within a few days' march, the city looked to its defenses, and Theodosius II built in 413–414 the 18 metre (60 ft) tall triple-wall fortifications which were never to be breached until the coming of gunpowder. Theodosius also founded a University near the Forum of Taurus, on 27 February 425.
Uldin, a prince of the Huns, appeared on the Danube about this time and advanced into Thrace, but he was deserted by many of his followers, who joined with the Romans in driving their king back north of the river. Subsequently new walls were built to defend the city, and the fleet on the Danube improved.
In due course the barbarians overran the Western Roman Empire: its emperors retreated to Ravenna, and it diminished to nothing. Thereafter, Constantinople became in truth the largest city of the Roman Empire and of the world. Emperors were no longer peripatetic between various court capitals and palaces. They remained in their palace in the Great City, and sent generals to command their armies. The wealth of the eastern Mediterranean and western Asia flowed into Constantinople.