Switzerland, the year is 325 AD. Constant attacks by the Alemanni tribes to the north have the occupying Romans on edge. Several decades before, between 259-275, the Roman colonia of Aventicum was sacked and almost destroyed in its entirety. Around the same time, the settlement at Yverdons was ravaged. Many other settlements suffered a similar fate.  

The town of Eburodunum, today’s Yverdon-les-Bains, sits on the edge of Lake Neuchatel, and in Roman times was an important trade and communications hub. Not to mention, its renowned thermal springs, from where the modern name is derived, provided a welcome relief for its residents.  

In 325, after several centuries of Roman occupation, emperor Constantine ordered a fort to be constructed as part of a wider defensive network. His reign was not only marked by his famed conversion to Christianity, but also by the continuation of a military and administrative overhaul which had begun under his predecessor Diocletian. Intended to solidify Rome’s imperial integrity, this restructuring was a direct response to the scale of the threat the empire faced. Between 325 and 326, the work began and likely took many years to complete.  

What had once been a largely civil settlement, dedicated to trade and transport, was almost entirely erased. From then on, the focus was military. Only two buildings survived the purge: the thermal baths and an audience hall, which was converted to use by the military. And the inhabitants? They were sent to find make a living elsewhere within Roman Switzerland.  

The resulting castrum enclosed a space of around two hectares and consisted of 15 large stone towers to defend against any attack.  

Today, little remains of the castrum. That it was the one of the largest, and most important, Roman settlements in Switzerland is nearly lost upon visiting it today. Scattered ruins litter the city, the Roman baths, a granary (pictured) and a few other scattered remains can be seen.  

After less than one hundred years, the Castrum was rendered useless, and its many years of construction futile. In 401, once again facing continuous attacks by the ‘barbarian’ menace, the emperor Honorius ordered the return of Rome’s troops across the Empire’s northern borders to return to Italy. The Castrum was abandoned that same year. Over time, the civilian population who had been expulsed returned and others moved in, resettling the military camp. Rome’s dominion over Switzerland, which had been tenuous at best for several decades, was well and truly fading.