Trajan's Bridge

Trajan's Bridge was a massive Roman segmental arch bridge.

It crossed the lower Danube River. This river now forms the border between Serbia and Romania. The structure was a major feat of Roman engineering. It was the first bridge built over this part of the Danube. For over 1,000 years, it was likely the longest arch bridge in the world.

This bridge helped the Roman Empire expand its reach into new lands.

Emperor Trajan ordered the bridge to be built for a specific reason. He needed a way to move his legions and supplies into Dacia. The bridge was designed by the architect Apollodorus of Damascus. Construction began around 103 AD and finished in 105 AD. This was just before the Second Dacian War. The project was part of a larger plan to secure the border. This plan included digging canals to help ships navigate the river safely. It also included building defense posts and intelligence services.

Building such a large bridge required very clever engineering.

Apollodorus used a technique called river flow relocation. Engineers waited for a dry year when water levels were low. They dug a canal west of Kladovo to redirect the water downstream. This left the river bed almost completely dry. This allowed workers to build foundations directly on the ground. They used wooden caissons to help build the piers. A caisson is a watertight structure used to work underwater.

The bridge sat on twenty massive masonry pillars.

These pillars were spaced 50 meters apart. Workers drove wooden pillars into the river bed to create a foundation. They coated these with clay and then built the piers. The piers were made of bricks, mortar, and pozzolana cement. Pozolana is a special volcanic ash used to make very strong mortar. The hollow piers were filled with stones and then encased in Roman bricks. The top of the bridge used wooden arches made of oak wood.

Security was a major part of the bridge's design. At each end of the bridge, the Romans built a fort. On the south bank, they built the Pontes fort in 103 AD. This fort occupied several hectares and had thick ramparts. A civilian settlement, called a vicus, grew up around it later. A bronze head of Emperor Trajan was found there. It was once part of a statue at the bridge entrance. On the north bank, the Romans built the Drobeta fort. These forts ensured that anyone crossing the bridge had to pass through Roman camps.

We know exactly who helped build this wonder through historical clues. The Roman legions and cohorts carved their names into the bricks. For example, the IV Flavia Felix and VII Claudia legions worked there. Other groups included the V Macedonica and XIII Gemina legions. These bricks can still be found near the village of Kostol today. The victory in Dacia was so significant it changed Roman history. The conquest led to the acquisition of gold mines. Celebrations for the victory lasted for 123 days. During these games, 10,000 gladiators fought and 11,000 wild animals were killed.

Time and nature eventually changed the bridge.

Trajan's successor, Hadrian, dismantled the wooden superstructure. He likely did this to stop barbarian invasions from the north. The wooden parts were later destroyed by fire. The bridge's remains were seen again in 1858 during a major drought. In 1906, two pillars were destroyed to help ships pass. Today, only the entrance pillars remain visible on the river banks. One is in Romania and one is in Serbia.

The bridge remains a protected historic monument in both countries.