Roman bridges

The Romans were the first to build large, permanent bridges. They built them of timber, as pontoons and, from the 2nd century BC, of stone, on the arch; most of the stone bridges used concrete, its first use in bridge-building. The state built bridges for the army and the running of the empire; for trade, boats usually served better (en.wikipedia).

The bridges in this atlas crossed the lower Danube, and of each a pier survives on the Romanian bank. Trajan’s Bridge, designed by his architect Apollodorus of Damascus and completed in 105, was the first bridge over the lower Danube, built so that Roman troops could cross into Dacia. It was 1,135 m long, with wooden arches on twenty masonry piers and a fort at each end, and Hadrian later had its wooden superstructure dismantled. One of its entrance piers stands beside the fort of Drobeta in Drobeta-Turnu Severin; the other is on the Serbian bank (en.wikipedia).

Constantine’s Bridge was opened on 5 July 328 in the emperor’s presence and ran from Sucidava, at today’s Corabia, to Oescus on the far bank, in modern Bulgaria. It was 2,434 m long overall, 1,137 m of it over the riverbed, the longest ancient river bridge, and it stayed in use for about four decades (en.wikipedia). One of its piers can still be seen near the late Roman fortress of Sucidava (de.wikipedia).