Trajan's Bridge over the Danube
About
Designed by Trajan's chief engineer Apollodorus of Damascus and built in just two years (103-105 CE) to move Roman forces across the lower Danube for the Second Dacian War, this was for over a millennium the longest arch bridge ever built — roughly 1,135 meters long, twenty masonry piers up to 19 meters high carrying wooden arches spanning about 38 meters each. At the exact moment this map is frozen, its wooden superstructure was almost certainly still standing: Cassius Dio records that Hadrian had it dismantled shortly after becoming emperor, so its destruction falls right at or just after 11 August 117 CE. The twenty masonry piers survived far longer and remain traceable archaeologically today.
What happened here
Piers are set on cofferdams — a ring of driven piles, pumped dry, filled with concrete that sets under water. They are built with a cutwater pointing upstream to split the current and the ice. The span above may be stone arches or timber on stone, and timber is not a poor relation: it is cheaper, faster, and replaceable. Roads approach on an embankment so the crossing stays level. Tolls are common, shrines at either end are usual, and the inscription names whoever paid. Floods are the enemy; a bridge is inspected after every big one, and the scour around the piers is packed with rubble. A bridge fixes a town's position for a thousand years, which is why so many are still standing.
Sources
Nearby
Roman Maps shows the empire frozen at 11 August 117 CE, the day Trajan died — its moment of greatest territorial extent. Explore the full map →