FreightWaves Classics/ Infrastructure: Constantine’s Bridge spanned the Danube 

Budapest on the Danube. (Photo: thecruiseline.com)FreightWaves Classics profiles a bridge that was built nearly 1,700 years ago.

Budapest on the Danube. (Photo: thecruiseline.com)

The river

The Danube is one of the most famous rivers in the world, along with the Nile, the Yangtze, the Amazon and the Mississippi. Along their routes are places of great natural and man-made beauty, as well as key sites in human history and culture.

The Danube is the second-longest river in Europe. Its path takes it through much of central and southeastern Europe, from the Black Forest into the Black Sea. The river makes its way through 10 nations – more than any other river in the world. The Danube begins in Germany and flows southeast for 1,770 miles. Along its route, it passes through or borders Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine before draining into the Black Sea. The river’s drainage basin extends into nine more countries. Many European borders, especially in the Balkans, also follow the route of the Danube.

The route of the Danube through Europe. (Image: Public Domain/commons.wikimedia.org)
The route of the Danube through Europe. (Image: Public Domain/commons.wikimedia.org)

Vienna, Budapest, Belgrade and Bratislava are among the largest cities on the Danube. They are also the capitals of their respective countries, which also means that the river passes through more national capitals than any other river in the world. In addition, five more capital cities lie in the Danube’s basin – Bucharest, Sofia, Zagreb, Ljubljana and Sarajevo. 

Interestingly, it’s not called the Danube in any of the countries it passes through. For example, in Germany the river is called the Donau, the Dunaj in the Czech Republic, and the Duna in Hungary. The Romans called it Danubius, based on an older Celtic name from which all the modern names are derived.

This map shows the darker area that encompasses the Danube's basin. (Image: CC BY-SA 4.0/ commons.wikimedia.org)
This map shows the darker area that encompasses the Danube’s basin. (Image: CC BY-SA 4.0/ commons.wikimedia.org)

The Danube divided nations and provide a route for commerce

The banks of the Danube have been the site of human habitation for millennia, and the river has been instrumental in many historical events and has defined historical borders. For almost its entire length the Danube was once the northern border of the Roman Empire. It provided a defensive line for the empire, as well as a “water highway” to transport troops and materials to Roman settlements downstream.

After the fall of the Roman Empire, the Danube continued to provide a defensive border for the  Eastern Roman Empire and then for the Ottoman Empire. The river’s separation between East and West would define the river’s story for centuries, particularly through World War I, World War II and the Cold War.

Since ancient times, the Danube also has served as a traditional trade route in Europe. Today, over 1,500 miles of its total length are navigable. In addition, the Danube is now linked to the North Sea via the Rhine-Main-Danube Canal, which connects the Danube at Kelheim with the Main at Bamberg. The river is also an important source of hydropower, drinking water and food. 

The Danube in Vienna. (Photo: Dmitry A. Mottl/commons.wikimedia.org)
The Danube in Vienna. (Photo: Dmitry A. Mottl/commons.wikimedia.org)

Constantine the Great

Constantine I (February 27, 272 – May 22, 337), also known as Constantine the Great, was the emperor of the Roman Empire from 306 to 337 AD. He was the first Roman emperor to convert to Christianity. Born in what is now Niš, Serbia, Constantine was the son of Flavius Constantius, a Roman army officer who had been one of the four rulers of the Tetrarchy. The Tetrarchy was the system instituted by Roman Emperor Diocletian in 293 to govern the ancient Roman Empire by dividing it between two senior emperors, and two junior emperors. The Tetrarchy marked the end of the Crisis of the Third Century. Constantine served with distinction under Diocletian and Galerius. His career as a soldier began in campaigns in the eastern provinces (against barbarians and the Persians). Then in AD 305 he was recalled to fight with his father in Britain. 

A modern bronze statue of Constantine I in York, England, near the spot where he was proclaimed emperor in 306. (Photo: Chabe01/wikipedia.org)
A modern bronze statue of Constantine I in York, England, near the spot where he was proclaimed emperor in 306.
(Photo: Chabe01/wikipedia.org)

After his father’s death in 306, Constantine became emperor. He was acclaimed by the Roman legions at Eboracum (now York, England), and eventually was victorious after civil wars against emperors Maxentius and Licinius. Constantine became the sole ruler of the Roman Empire by 324.

Following his ascension to emperor, Constantine began a series of reforms to strengthen the empire. He separated civil and military leaders, restructuring the government. To combat inflation, he introduced a new gold coin (the solidus, which was also known as the nomisma or the bezant). Constantine introduced the coin, and its weight of about 4.5 grams remained relatively constant. It became the standard for Byzantine and European currencies for more than 1,000  years. 

A solidus with an image of Constantine. (Photo: educalingo.com)
A solidus with an image of Constantine. (Photo: educalingo.com)

Constantine also reorganized the Roman legions into two different forces – mobile units (comitatenses) and garrison troops (limitanei) – to make the army more capable of countering internal threats and barbarian invasions. Constantine then pursued successful military campaigns against various tribes on the Roman frontiers (such as the Franks, the Alamanni, the Goths and the Sarmatians). He then resettled territories abandoned by his predecessors during the Crisis of the Third Century with citizens of Roman culture.

Parts of a giant statue of Constantine. (Photo: Khan Academy)
Pieces of a giant statue of Constantine. (Photo: Khan Academy)

Although Constantine lived much of his life as a pagan, he began to favor Christianity in 312. He became a Christian and was baptized. Constantine played a key role in the Edict of Milan in 313, which declared tolerance for Christianity in the Roman Empire. He also convened the First Council of Nicaea in 325; it produced the statement of Christian belief known as the Nicene Creed. On his orders, the Church of the Holy Sepulchre was constructed at the purported site of the tomb of Jesus in Jerusalem and was deemed the holiest place in all of Christendom. Constantine has historically been referred to as the “First Christian Emperor” and is recognized for moving Christianity towards the mainstream of Roman culture.

Constantine’s rule was a distinct era in the history of the Roman Empire; many consider that he began the transition of the empire from classical antiquity to the Middle Ages. Among his actions, he built a new imperial residence in Byzantium and renamed it Constantinople (now known as Istanbul) after himself. Constantinople subsequently became the new capital of the empire for more than 1,000 years. The later Eastern Roman Empire is termed the Byzantine Empire by modern historians. He replaced Diocletian’s Tetrarchy; Constantine established the principle of dynastic succession, leaving the empire to his sons and other members of the Constantinian dynasty. 

The northern and eastern frontiers of the Roman Empire in the time of Constantine, with the territories acquired in the course of the 30 years of military campaigns between 306 and 337. (Image: Cristiano64/commons.wikimedia.org)
The northern and eastern frontiers of the Roman Empire in the time of Constantine, with the territories acquired in the course of the 30 years of military campaigns between 306 and 337. (Image: Cristiano64/commons.wikimedia.org)

July 5, 328

A bridge built across the Danube made its formal debut on this date 1,694 years ago. Constantine was present for the opening of the bridge, which became known as Constantine’s Bridge. It was built between the town and fortress of Sucidava (now the Romanian port town of Corabia) and the town of Oescus (near the present-day Bulgarian village of Gigen).

Roman architect Theophilus Patricius designed Constantine’s Bridge. Among the key architectural features of the wooden arch bridge were its masonry piers and wooden superstructure. It also had two abutment piers at each end. “Abutments are used at the ends of bridges to retain the embankment and to carry the vertical and horizontal loads from the superstructure to the foundation.” The abutments also served as gates for the bridge, helping to protect it from attack at either end. The bridge’s wooden deck was 19 feet wide and crossed the river 33 feet above the water.

Carnuntum Archaeological Park at Petronell: remains of an inn between reconstructed public baths (left) and a large urban house (right). The  inset is the "hypocaust" (heating system) in the baths. This 4th century outpost was near the River Danube and the border between Austria and Slovakia. (Photo: Roberto Piperno)
Carnuntum Archaeological Park at Petronell: remains of an inn between reconstructed public baths (left) and a large urban house (right). The inset is the “hypocaust” (heating system) in the baths. This 4th century outpost was near the River Danube and the border between Austria and Slovakia. (Photo: Roberto Piperno)

While the bridge was destroyed within 50 years of its construction, it is still remembered today because of its overall length of 7,995 feet. Of that length, 3,730 feet spanned the Danube’s riverbed. Constantine’s Bridge was the longest ancient river bridge and one of the longest of all time.

The Dacian kingdom in 82 BC. 
(Image: commons.wikimedia.org)
The Dacian kingdom in 82 BC.
(Image: commons.wikimedia.org)

A key reason for the construction of Constantine’s Bridge was the effort to reconquer Dacia. A Dacian kingdom of variable size existed between 82 BC until the Roman conquest in AD 106. The capital of Dacia was located in modern Romania; it was destroyed by the Romans, but the same name was used by the Romans for the new city built as the capital of the Roman province of Dacia. 

As the Roman Empire weakened, the Dacians overthrew their Roman rulers until Constantine again conquered the area. The Dacian kingdom included the present-day countries of Romania and Moldova, as well as smaller parts of Bulgaria, Serbia, Hungary, Poland, Slovakia and Ukraine.