What Roman bridge over the Danube River was built by Emperor Trajan in 105 AD?

The Roman bridge over the Danube built under Emperor Trajan in AD 105 is Trajan’s Bridge.

Also called the Bridge of Apollodorus, it was designed by Apollodorus of Damascus for Rome’s campaigns against Dacia. The bridge linked the Roman fort at Drobeta, in present-day Romania, with Pontes on the Serbian bank. Its purpose was strategic: it provided a permanent route for troops and supplies across the lower Danube during the Second Dacian War.

Trajan’s Bridge stretched about 1,135 metres and rested on twenty masonry piers. Its superstructure used wooden segmental arches, an unusual combination of timber and substantial Roman concrete-and-brick foundations. The bridge remained functional for roughly 165 years before its upper structure was destroyed around the time Rome abandoned Dacia under Emperor Aurelian. Fragmentary piers and approach remains still mark the site. It is not the Pont du Gard, which was primarily an aqueduct, nor the Pons Aemilius, an earlier bridge in Rome.