The city of Cologne possessed distinctive features and phases from its beginnings that should be more fully considered in the balance of any urban history of medieval Europe. As a creation of Roman city planning, it consistently bore the marks of imperial patronage (both for good and for ill) and evolved thereby from an agro-town (oppidum) into Roman colony (CCAA), a legally recognized city (civitas), and finally a provincial capital (caput provinciae). Yet it also bore from its very genesis the distinctive marks of collaboration between Romans and Germanic peoples. As a frontier urban settlement, Cologne provided a space where Romans from across the empire met Germanic peoples from the Ubians to the Franks and assimilated with them socially, economically, religiously, culturally, and politically. Indeed, we miss a significant aspect of the city's manufacturing and trade activity when we only expect to find how it connected Cologne residents with the wider Roman world while neglecting the ties created over generations with the other shore of the Rhine River.

Roman citizens from virtually every point in the empire either settled or were stationed and then retired with their families in Cologne and its vicinity, all the while sharing streets, markets, altars, families, farms, and military commissions with Ubians and members of the Frankish confederation. The Ubian refusal to sacrifice their own Roman relatives and fellow citizens during the Batavian siege of the city in A.D. 69 was an early witness to this assimilation process. And when Ripuarian Frankish desire to live in Cologne and its environs became irresistible by the mid-fourth century, accommodation to this later-day emigrant confederation defined Roman provincial policy. Finally, as this frontier zone became unreservedly open to the Ripuarian Franks by the mid-fifth century, the new settlers came in fuller numbers not as destroyers of Romanitas but as Germanic peoples quite familiar with the Gallo-Romans and the benefits of life in the Rhine-Maas corridor. Cologne itself certainly experienced thereby a permanent change in the ruling elite of its community, but this transition had been well underway for at least a century. The city and its hinterlands were not destroyed but occupied, as an area to be inhabited and cultivated rather than burned and buried.