Roman Bridge of Chaves · Wikimedia Commons

Roman Bridge of Chaves

Pons Traiani (Aquae Flaviae)

BridgeHispania Tarraconensis · Chaves, Vila Real District, PortugalBuilt 104 CE

About

A 140-meter granite bridge over the Tamega carried the road linking Bracara Augusta (Braga) and Asturica Augusta (Astorga) through Aquae Flaviae, a spa town whose thermal springs made it a municipium under Vespasian. Two inscribed columns stand on the bridge: an earlier one (79 CE) honoring Vespasian and Titus, and a Trajanic column of 104 CE recording that the local populi of the surrounding conventus paid for and dedicated the bridge — a rare direct epigraphic record of provincial communities funding Roman infrastructure. Aquae Flaviae sat in the Conventus Bracaraugustanus of Hispania Tarraconensis in 117 CE; the later separate province of Gallaecia was not split off until after Diocletian.

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.

In ancient writing

CIL, II 2477
The Padrao dos Povos, a dedicatory inscription set up at the bridge naming ten local Gallaecian civitates that contributed to its construction, dated to Vespasian's reign.