Trajan's Plaque

Trajan's Bridge, also called Bridge of Apollodorus over the Danube, was a Roman segmental arch bridge, the first bridge to be built over the lower Danube and considered one of the greatest achievements in Roman architecture. Though it was only functional for 165 years, it is often considered to have been the longest arch bridge in both total span and length for more than 1,000 years.

The bridge was completed in 105 AD and designed by Emperor Trajan's architect Apollodorus of Damascus before the Second Dacian War to allow Roman troops to cross the river. Fragmentary ruins of the bridge's piers are still in existence.

Source: Wikipedia