When Emperor Hadrian destroyed the longest bridge in the world

In the year 103 AD, Emperor Trajan ordered the construction of a bridge over the Danube River that would serve to cross and supply the troops in the imminent Second Dacian War against Decebalus, for which he was preparing the largest army since the time of Augustus, some 150,000 men.

The person in charge of projecting and erecting it was the architect Apollodorus of Damascus, to whom the Pantheon is also attributed, and who was the emperor’s favorite architect since his are also the baths, the forum, the market and Trajan’s column.

It was situated near the modern Romanian town of Drobeta-Turnu Severin, east of the Iron Gates, the natural canyon of the Danube that runs parallel to the border with Serbia. Its construction ended in the year 105 AD, constituting one of the most outstanding engineering works of antiquity.

The bridge represented in the Trajan Column / photo public domain in Wikimedia Commons

It was 1,135 meters long by 14.55 meters wide and 18.60 meters high from the water, in an area where today the river is 800 meters wide. It extended on 20 masonry pillars of brick, mortar and pozzolanic cement joined by segmental arches of oak wood at intervals of 50 meters.

The bricks that make up the pillars, some of which have been found, have great historical value, as the soldiers who participated in their construction carved the names of their units on them.

One of the bricks with the name of the legion / photo Danube Virtual Museum

For this reason, it is known that the legions IV Flavia Felix, VII Claudia, V Macedónica and XIII Gémina participated in the construction of the bridge, as well as cohorts from I Cretum, II Hispanorum, III Britorum and I Antiochensium.

On both sides of the bridge rose two castrate (fortified camps, singular castrum), so that to cross the bridge it was necessary to cross the castrateremnants of which are still visible today.

We know what the bridge looked like from classical sources, and especially from Dio Cassius who, in his roman history details its technical characteristics. But also because his representation appears on the Trajan column in Rome.

Remains of the bridge today / photo DjordjeMarkovic on Wikimedia Commons

Still today, both on the Serbian and Romanian shores, the remains of the vaulted arcades that gave access to the bridge can be seen.

Trajan built a stone bridge over the Ister that overwhelms my admiration for him. In fact, although he was brilliant in all his exploits, this was the greatest. It has twenty square stone pillars one hundred and fifty feet high from the foundations and sixty wide; they are situated at intervals of one hundred and seventy feet and linked by arches. How can anyone fail to be amazed at the great investment that was made, or at the way each of these pillars was anchored so deeply in a river whose waters are full of backwaters and with such a muddy bottom?

Cassius Dio, roman history 68.13 (Translation by Pilar González-Conde)

Although the bridge was only functional for a few decades, for more than 1,000 years it was the longest arch bridge in the world. It is not known exactly when, but there is evidence that the emperor Hadrian ordered the demolition of its upper structure to prevent the barbarians from crossing it.

Reconstruction of one of the arches on the Romanian shore / photo Carole Raddato on Wikimedia Commons

Some historians believe that it was only a temporary measure, and that the bridge could be used again during the reigns of Diocletian and Constantine. The Byzantine writer Procopius wrote that by his time, the 6th century AD, the bridge was already in ruins.

At the same time, one of the circumstances that shows the greatness of Trajan’s plans is that the bridge was not made to be used by us; the mere presence of the upright pillars, although no attempt is made to cross it, suggests that they were erected for the sole purpose of demonstrating that there is nothing that human ingenuity cannot achieve. Trajan built the bridge because he feared that if the Ister ever froze over in the middle of a war he might surprise the Romans on that bank, and it was necessary to secure access to them by these means. On the contrary, Hadrian was afraid that he, too, might make the passage easy for the barbarians, who after defeating the bridge guard might cross into Moesia; therefore, he dismantled this great structure.

Cassius Dio, roman history 68.13 (Translation by Pilar González-Conde)

The pillars were submerged, reappearing in 1858 due to the drought that lowered the flow of the river to levels never seen before. Two of them were shot down in 1906 to facilitate navigation. In 1932 there were 16 pillars left, but in 1982 only 12 could be found, possibly the others were dragged by the current.


Danube Virtual Museum / Cervantes Virtual / Roman Woodworking (Roger Bradley Ullrich) / A Dictionary of Greek and Roman Geography (William Smith) / Wikipedia.

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