Pont Julien, Bonnieux · Wikimedia Commons

Pons Iulius

Pont Julien

BridgeGallia Narbonensis · Bonnieux, FranceBuilt 3 BCE

About

Roman engineers raised this limestone bridge around 3 BCE to carry the Via Domitia, the oldest Roman road in Gaul, across the seasonal Calavon river. Three arches span 85 meters, with the central arch alone stretching over 16 meters, and the builders cut rectangular openings straight through the piers so floodwater could pass without toppling the structure. The design worked so well that the bridge still carried ordinary car traffic until 2005, more than two thousand years after the last Roman legionary crossed it. Travelers moving between Italy and Spain along the Via Domitia in 117 CE would have crossed this exact span west of Apt.

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.