Roman Rhine Bridge at Mogontiacum
About
A major fixed bridge across the Rhine linking the legionary fortress and civilian settlement at Mogontiacum to the fort of Castellum Mattiacorum on the far bank. An initial pontoon or timber crossing existed from around 11 BCE, but the permanent bridge — some 21 stone piers spanning roughly 400 meters — is generally dated to c. 71 CE, in the early Flavian period after the Batavian Revolt, when Rome moved to secure the crossing permanently. It remained standing into the early 5th century, well beyond 117 CE. Some popular accounts credit Domitian, but the stone construction is more consistently dated to 71 CE under Vespasian.
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
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