From an Ancient Greek Settlement to the Capital of an Empire
The words Byzantium, Constantinople, and Byzantine Empire are closely connected, but they do not mean exactly the same thing.
Byzantium was originally the name of an ancient Greek settlement established on the site that would eventually become Constantinople and, centuries later, modern Istanbul. Constantinople became the capital of the Roman Empire under Constantine the Great, while the expression “Byzantine Empire” was developed by historians much later to describe the medieval Eastern Roman Empire centered on Constantinople.
This distinction is important because the people we now call Byzantines did not normally describe themselves as Byzantines. They considered themselves Romans, and their empire was understood as the Roman Empire.
So how did an ancient settlement called Byzantium give its name to an empire whose inhabitants never actually called it the Byzantine Empire?
The story begins almost a thousand years before Constantine.
What Was Byzantium?
Byzantium, known in Greek as Byzantion, was an ancient Greek settlement established in the 7th century BC on the European side of the Bosphorus.
Its location was exceptional.
The settlement occupied a strategically protected peninsula surrounded by the Bosphorus, the Golden Horn, and the Sea of Marmara. From this position, its inhabitants could participate in maritime trade while controlling an important passage between the Mediterranean and Black Sea worlds.
According to ancient tradition, Byzantium was founded by Byzas, a legendary leader associated with settlers from Megara.
The best-known foundation story involves the Oracle of Delphi.
According to the legend, Byzas was instructed to establish his settlement opposite the “land of the blind.” When he reached the Bosphorus, he saw an existing settlement at Chalcedon on the Asian shore, near present-day Kadikoy. Looking across the water toward the naturally protected peninsula on the European side, he supposedly concluded that the earlier settlers must have been “blind” not to have chosen the superior location.
Whether or not the story reflects historical events, it expresses something that would shape the city’s history for more than two thousand years:
location mattered.
The extraordinary geographical position of Byzantium would eventually help transform a relatively small ancient settlement into one of the most important cities in world history.
Byzantium Before Constantine
Byzantium existed for centuries before it became an imperial capital.
Its strategic location also meant that it frequently became involved in conflicts between larger powers. Persians, Greek city-states, Macedonians, and eventually Romans all influenced or controlled the settlement at different periods.
Byzantium ultimately became part of the Roman world.
One particularly dramatic episode occurred during the civil wars of the late 2nd century AD, when the city supported Pescennius Niger against the Roman emperor Septimius Severus. After a prolonged siege, Byzantium was severely punished, although Severus later rebuilt important parts of the city.
Even then, however, nobody could have anticipated what Byzantium was about to become.
Its decisive transformation came in the 4th century under Constantine the Great.
Why Did Constantine Choose Byzantium?
During the early 4th century, the Roman Empire was undergoing enormous political and religious change.
After defeating his rival Licinius in 324 AD, Constantine became the sole ruler of the Roman Empire. He then began transforming Byzantium into a new imperial residence and capital.
The location offered several advantages.
It occupied a defensible peninsula, controlled the Bosphorus, stood between Europe and Asia, and provided access to important commercial and military routes. It was also strategically positioned closer than Rome to many of the empire’s increasingly important eastern territories and frontiers.
Constantine dramatically expanded the old city, constructing palaces, forums, public buildings, baths, churches, and a much larger defensive system.
On May 11, 330 AD, the new imperial capital was formally inaugurated.
The city was associated with the idea of New Rome, but the name that endured was Constantinople — the City of Constantine.
The small ancient settlement of Byzantium had become the center of an empire.
Was Constantine the First Christian Emperor?
Constantine occupies a crucial place in the history of Christianity, but his religious story is more complicated than simply calling him the first Christian emperor.
Christianity had experienced periods of severe persecution under earlier Roman emperors, particularly during the reign of Diocletian and his colleagues.
Constantine dramatically changed the position of Christians within the empire.
Together with Licinius, he supported the policy traditionally associated with the Edict of Milan in 313, which established religious toleration and restored property previously confiscated from Christians.
Constantine subsequently supported the Church, sponsored major Christian buildings, granted privileges to Christian clergy, and became deeply involved in ecclesiastical affairs. He also convened the Council of Nicaea in 325, one of the most important councils in Christian history.
Nevertheless, Christianity did not become the official religion of the Roman Empire under Constantine.
That development came later, particularly under Emperor Theodosius I toward the end of the 4th century.
Constantine’s reign nevertheless represented a profound turning point. Christianity moved from a persecuted religion to one increasingly connected with imperial power, while Constantinople would eventually develop into one of the greatest centers of Christianity.
Constantinople and the Roman Empire
Constantinople’s importance grew rapidly after its foundation.
Following the death of Theodosius I in 395, imperial administration was permanently divided between eastern and western courts. The eastern territories were governed from Constantinople, while the western empire faced increasingly serious political and military pressures.
The Western Roman Empire did not suddenly disappear in a single event.
Rome itself was famously sacked by the Visigoths in 410, but western emperors continued to rule for several more decades. The conventional date for the end of the Western Roman Empire is 476 AD, when the last western emperor, Romulus Augustulus, was deposed.
The Roman Empire in the east, however, continued.
Its inhabitants did not believe that Rome had fallen and been replaced by an entirely new Byzantine civilization.
For them, their empire was Roman.
Constantinople had become the political center of a Roman state that would survive for almost another thousand years.
So What Was the Byzantine Empire?
The expression Byzantine Empire is a modern historical convention.
The people whom historians today call Byzantines generally identified themselves as Romans, and their state continued Roman political and imperial traditions.
Over the centuries, however, the eastern empire developed characteristics that distinguished medieval Constantinople considerably from the ancient Roman world.
Greek gradually became dominant in administration and culture. Christianity became fundamental to imperial identity. Roman institutions evolved, territories changed, and the empire developed distinctive artistic, theological, architectural, and political traditions.
Modern historians therefore use the term Byzantine Empire to distinguish the medieval Eastern Roman Empire from earlier periods of Roman history.
The name derives from Byzantium, the ancient settlement upon which Constantinople had been built.
The terminology became established among western European scholars centuries after the empire itself had disappeared and became increasingly common in modern historical writing.
So although “Byzantine Empire” is extremely useful today, a visitor to medieval Constantinople would not have encountered people introducing themselves as Byzantines.
They were Romans living in the Roman Empire.
Was the Byzantine Empire Really Roman?
Yes—but the answer requires some historical perspective.
The Byzantine Empire was not a separate state suddenly created when the Roman Empire divided.
There was considerable institutional continuity between the ancient Roman Empire and the medieval empire centered on Constantinople. Its rulers considered themselves Roman emperors, its inhabitants used Roman political identity, and Roman law remained fundamental to the state.
One of the clearest examples comes from the reign of Emperor Justinian I in the 6th century.
Justinian ordered the great codification of Roman law known today as the Corpus Juris Civilis, or Body of Civil Law. Its influence extended far beyond Byzantium and later became enormously important in the development of European legal traditions.
At the same time, the empire changed substantially over its long history.
A resident of Constantinople in the 12th century lived in a society very different from that of Rome under Augustus. Language, religion, government, warfare, culture, and territorial boundaries had all evolved.
Calling the empire “Byzantine” therefore helps historians discuss these later centuries while recognizing that its inhabitants themselves maintained a Roman identity.
Constantinople: Capital of the Byzantine World
For much of the Middle Ages, Constantinople was one of the largest, wealthiest, and most sophisticated cities in the Mediterranean world.
Its position allowed it to control trade routes between Europe and Asia and between the Black Sea and Mediterranean.
Massive fortifications protected the capital.
The most famous were the Theodosian Walls, constructed principally during the reign of Theodosius II in the 5th century. With multiple defensive lines, towers, and a moat, they formed one of the most formidable urban defense systems of the medieval world.
Inside the walls stood imperial palaces, churches, monasteries, markets, cisterns, forums, baths, and public monuments.
The Hippodrome served as a center for chariot racing, imperial ceremony, and public political life.
The city’s enormous water infrastructure included aqueducts and hundreds of cisterns, among them the famous Basilica Cistern.
Above all, Constantinople became one of the principal centers of Christianity.
Its churches and monasteries shaped religious, intellectual, and artistic life across the Christian East.
Justinian and the Age of Hagia Sophia
One of the most famous periods of Byzantine history came during the reign of Emperor Justinian I, from 527 to 565.
Justinian attempted to restore imperial authority over former western Roman territories and his armies reconquered substantial parts of North Africa, Italy, and sections of the western Mediterranean.
His reign also produced major legal and architectural achievements.
Nothing symbolizes Justinian’s Constantinople more powerfully than Hagia Sophia.
The present structure was commissioned after the destruction of an earlier church during the Nika Revolt of 532. Designed by Anthemius of Tralles and Isidore of Miletus, the enormous new church was completed in less than six years and inaugurated in 537.
Its vast dome and innovative structural design made it one of the greatest architectural achievements of Late Antiquity.
For nearly nine centuries, Hagia Sophia served as the principal imperial church of Constantinople, although its history included interruptions and major changes.
Its architecture would later influence both Christian and Ottoman religious architecture and remains one of the most extraordinary surviving monuments of the Byzantine world.
Christianity in the Byzantine Empire
Christianity became inseparable from Byzantine political and cultural identity.
Constantinople developed into one of the great centers of the Christian world, and its bishop gradually acquired exceptional importance.
At the Council of Constantinople in 381, the bishop of Constantinople was given precedence of honor after the bishop of Rome, reflecting the status of the city as the imperial capital.
The relationship between emperors, bishops, patriarchs, monasteries, and theological movements was complex. Religious controversies could affect imperial politics, while emperors sometimes intervened directly in disputes concerning Christian doctrine.
Byzantine theologians, church fathers, monks, artists, and councils profoundly influenced the development of Eastern Christianity.
The city’s religious heritage remains visible today through monuments such as Hagia Sophia, the Chora Church, Hagia Irene, and the continuing presence of the Ecumenical Patriarchate of Constantinople.
Icons and the Iconoclast Controversy
One of the most important religious conflicts in Byzantine history concerned the use of sacred images.
During the 8th and 9th centuries, Byzantine society experienced periods of Iconoclasm, when imperial policies opposed the religious veneration of icons.
Images were removed, destroyed, or replaced in some churches, while supporters of icons defended their use in Christian worship.
The controversy involved theology, imperial authority, monastic communities, and wider questions about the representation of the sacred.
The restoration of icons in 843 became celebrated in the Eastern Orthodox tradition as the Triumph of Orthodoxy.
Byzantine iconography subsequently developed into one of the empire’s most enduring artistic traditions, influencing Orthodox Christian art from the Balkans and Russia to the eastern Mediterranean.
Byzantine Art and Architecture
The artistic legacy of Byzantium extends far beyond Istanbul.
Byzantine artists developed sophisticated traditions of mosaics, frescoes, icons, manuscript illumination, metalwork, ivory carving, and church architecture.
Religious art was intended not merely as decoration but as a visual expression of theology.
Gold-background mosaics, monumental images of Christ and the Virgin Mary, saints, emperors, biblical scenes, and carefully structured church interiors created sacred environments designed to connect earthly worship with the heavenly realm.
Istanbul preserves extraordinary examples.
The mosaics of Hagia Sophia include imperial and religious imagery from different periods, while the mosaics and frescoes of the Chora Church represent some of the finest surviving achievements of late Byzantine art.
Even after the Byzantine Empire disappeared, its artistic traditions continued throughout the Orthodox Christian world.
The Great Schism of 1054
Relations between the churches of Rome and Constantinople became increasingly complicated over many centuries.
Differences developed over theology, ecclesiastical authority, language, liturgical practices, and politics.
The events of 1054, when representatives of Pope Leo IX and Patriarch Michael Keroularios exchanged excommunications, are traditionally associated with the Great Schism between the Roman Catholic and Eastern Orthodox Churches.
The separation was not simply the result of a single event, and relations had experienced disputes and reconciliations before and after 1054.
Nevertheless, the growing division between Latin Christianity in the West and Greek-speaking Orthodox Christianity in the East became one of the defining developments of medieval Christian history.
The relationship deteriorated dramatically during the Crusades.
The Fourth Crusade and the Sack of Constantinople
One of the greatest catastrophes in Byzantine history came not from an Islamic army but from western European Crusaders.
The Fourth Crusade, originally intended for campaigns elsewhere, became entangled in Byzantine dynastic politics.
In 1204, Crusader forces captured and brutally sacked Constantinople.
Churches, palaces, and other buildings were looted. Works of art and religious relics were taken westward, while many others were destroyed or lost.
A Latin Empire was established in Constantinople, and Byzantine successor states emerged elsewhere.
In 1261, forces of the Empire of Nicaea recovered Constantinople and restored Byzantine rule under the Palaiologos dynasty.
But the restored empire was much weaker than the state that had existed before 1204.
The Fourth Crusade left deep political, economic, cultural, and religious scars and remains one of the major turning points in the history of Constantinople.
The Final Centuries of Byzantium
During its final centuries, the Byzantine Empire faced shrinking territory, economic difficulties, internal political conflicts, and increasingly powerful neighboring states.
By the 15th century, the empire that had once ruled vast territories had been reduced largely to Constantinople and a limited number of other possessions.
Yet Constantinople remained enormously important symbolically.
It was still the city of Constantine, the seat of the Byzantine emperor, and one of the greatest centers of Orthodox Christianity.
Meanwhile, the Ottoman Empire had expanded across Anatolia and southeastern Europe, leaving Constantinople increasingly surrounded by Ottoman territory.
The final confrontation came during the reign of Sultan Mehmed II.
The Fall of Constantinople in 1453
In the spring of 1453, Mehmed II began the siege of Constantinople.
The city’s defenders, led by the last Byzantine emperor, Constantine XI Palaiologos, faced a much larger Ottoman force equipped with powerful artillery.
After approximately seven weeks of siege, Ottoman forces broke through the city’s defenses on May 29, 1453.
Constantine XI died during the final fighting, and Constantinople passed into Ottoman control.
The conquest ended the Byzantine imperial state and brought the Roman imperial tradition centered on Constantinople to an end after more than eleven centuries.
For Mehmed II, however, Constantinople was not simply a defeated enemy city.
It became the capital of the Ottoman Empire.
The city was gradually repopulated and rebuilt, beginning another extraordinary chapter in its history.
Did the Roman Empire Really End in 1453?
If the Byzantine Empire is understood as the medieval continuation of the Roman Empire, then 1453 can indeed be regarded as the end of the Roman imperial state.
This sometimes surprises visitors because modern historical terminology creates the impression that the Roman and Byzantine empires were completely separate civilizations.
There was no moment when an emperor in Constantinople announced that the Roman Empire had ended and the Byzantine Empire had begun.
The transition was gradual.
The empire of Constantine, Justinian, the Macedonian emperors, the Komnenoi, and the Palaiologoi changed enormously over more than a thousand years, but its rulers and inhabitants continued to claim Roman identity.
The term “Byzantine Empire” allows us to describe this distinctive medieval civilization more easily.
Understanding that terminology, however, reveals something even more fascinating:
Byzantine history is also Roman history.
The Legacy of the Byzantine Empire
The Byzantine Empire disappeared politically in 1453, but its influence did not.
Byzantine Christianity profoundly shaped the Orthodox Christian world. Its missionaries, theologians, liturgy, art, and religious traditions influenced societies throughout southeastern and eastern Europe.
Byzantine law preserved and developed Roman legal traditions.
Its scholars copied and studied ancient Greek texts, helping preserve important works of classical literature, philosophy, science, and history.
Byzantine artistic traditions influenced architecture, mosaics, icons, church decoration, and religious culture across an enormous geographical area.
Its greatest city also survived.
Constantinople became Ottoman Istanbul, and the new rulers inherited a city whose streets, monuments, infrastructure, and geography had been shaped by more than a thousand years as an imperial capital.
Today, Byzantine Constantinople remains visible throughout Istanbul—in churches and cisterns, surviving sections of walls, archaeological remains, ancient columns, palace foundations, mosaics, and even the basic geography of the Historic Peninsula.
Discover Byzantine Istanbul Today
Modern Istanbul is one of the best places in the world to explore Byzantine history because the former imperial capital still contains monuments from many different periods of the empire.
Hagia Sophia reveals the architectural ambition of Justinian’s age. The Hippodrome preserves traces of the ceremonial and public center of Constantinople. The Basilica Cistern demonstrates the sophistication of the city’s water infrastructure, while the Theodosian Walls reveal the extraordinary defenses that protected the capital for centuries.
The Chora Church preserves some of the finest surviving examples of late Byzantine mosaics and frescoes, while the Istanbul Archaeological Museums contain objects that provide further insight into Constantinople and the wider Byzantine world.
Even where Byzantine buildings have disappeared, understanding the ancient topography can completely change the way visitors experience Istanbul.
Beneath the modern city lies the landscape of Constantinople.
Explore Byzantine Istanbul With a Private Guide
Discover the surviving monuments of Constantinople and experience the extraordinary story of the Byzantine Empire with your own private guide. From Hagia Sophia and the Hippodrome to the Basilica Cistern, Chora Church, and the ancient city walls, Istanbul offers remarkable opportunities to explore more than a thousand years of Byzantine history.
Whether you are interested in Roman history, Byzantine architecture, Christian history, emperors, mosaics, archaeology, or the transformation of Constantinople into Ottoman Istanbul, our private tours can be personalized around the subjects, monuments, and historical periods that interest you most.