Trier's Porta Nigra, its amphitheater, the austere basilica, the prodigious Imperial and Barbara Baths, “two of the largest sets of baths in the Empire outside Rome,” attest not only to the prosperity of this Roman outpost on the banks of the Moselle, but to the preeminence of the Roman Rhineland (see plate 2.1). It may be eccentric to begin a book on European Union with a chapter on Rome. But if, as I maintain, European Union is about deconstructing a discursively constructed frontier that bisects the heart of Europe's most vital regional economy, then it is not unreasonable to begin by asking how that frontier got there in the first place. By revisiting Caesar's campaign we witness the first mention of the Rhine frontier in text, and discover the political interests that motivated its enunciation. We can conduct an initial test of the referential power of the signifier “frontier” by exploring the nature of social relations that obtained there. From this exercise come three observations. First, the Rhine did not separate Gauls from Germans either before or after Caesar's proclamation. Second, Rome's systematic exploitation of the region's geographical endowments turned the Greater Rhineland into one of the most dynamic regional economies of the western empire. Third, the Greater Rhineland regional economy absorbed peoples beyond the limes and thus conditioned the atypical “invasion” by the Franks, who, unlike other “Germanic” tribes that migrated deep into Italy, Gaul, Spain, and north Africa, did not advance much beyond their Rhine basin home.