The longest bridge for 1000 years

In 105 AD an amazing engineering project was completed.  The Romans built a bridge over the Danube river.  This wasn't a temporary structure like previous pontoon bridges, this was 20 masonry piers that towered 60 feet above the water, high enough to allow boats to pass beneath.  It was 50 feet wide and reached an amazing 3700 feet long, spanning the river.  For 1000 years it was the longest permanent bridge in history.

The Roman Emperor Trajan was called Optimus ("The Best") by the Senate.  He embodied the great Roman virtues, not least of which was determination combined with careful planning that allowed him to push the Empire's borders to their maximum extent.  He had decided that the Dacians living north of the Danube had given Rome enough trouble, and that their lands (and especially their gold mines) would make a very nice addition to the Empire.  And so he sent the Legions across the new bridge.

As they say, amateurs talk strategy while professionals talk logistics.  Previous invasions by the Romans had faltered because it was too hard to keep the armies supplied.  The bridge took care of that, and Dacia was soon added to the list of Roman provinces.  If you go to Rome, you will find Trajan's Column in the Forum.  It depicts the events of the invasion, including showing the bridge itself:

This is the only depiction of the bridge from the time, but from descriptions we have a pretty good idea of what it looked like.  This is a pretty cool fly by video showing what it would have looked like at the time.


Trajan's Bridge from Dan Marino on Vimeo.

Designed by Trajan's favorite architect, Apollodorus of Damascus, it was built with famous Roman determination.  The entire Danube river was diverted via a canal while the piers were sunk into the river bed.  Once the piers were done, the river was returned to its course - except it was improved, as some rapids were bypassed by a new canal to improve navigation.  The Romans were nothing if not doggedly determined to remove all obstacles in their way.

But the new borders north of the Danube were, you might say, a bridge too far.  Trajan's successor Hadrian is now famous for his wall, but that was just one part of his effort to cement defensible borders.  He wanted to retreat from Dacia, but while he was successful withdrawing from others of Trajan's conquests, he was forced to keep Dacia.  There had been too much Roman blood spilled to take it (and the gold mines were far too profitable) to be able to leave.  It would be another 170 years before Aurelian finally withdrew south across the river, tearing down the bridge.  By that time the mines were exhausted and the Empire couldn't defend the exposed province.

A couple hundred years later the Romans began to lose the expertise needed to build a bridge like this, as the lamps began to flicker and go out across Europe for a millennium.  But the column in Rome is a reminder that the Grandeur of Rome was pretty grand at the time.