rather than on mountain ranges, which prevent it, were far from impervious to the influence of foreign cultures. Yet the degree of uniformity of language and culture
achieved within the empire, and the physical resources which made this uniformity possible, were extraordinarily impressive. Tacitus wrote of the Roman Empire as
encircled by rivers and seas, every part-armies, provinces, navies-joined together as one system, and he was right. It was a rhetorical theme, sustained to the end of
the Roman Empire, that Rome the city (urbs) had made the world (prbis) its own; conversely, that in Rome the city the entire world possessed a symbol of its
identity. A commonplace sentiment perhaps, but a real one, and one with practical (if sometimes unexpected) consequences. It was not permissible, for example, for
a man exiled from his own city to reside in Rome, for this was the 'common homeland' of all citizens. It is conventional to point to the sheer distances that were
involved in travel between provinces, and between Rome and the frontiers, to the constant dangers of sea journeys and the inevitable slowness (given the nature of
the available technology) of transport by land. But this is a relative matter; journeys like that of the Bordeaux pilgrim were undertaken, made possible by roads
driven through provinces, over passes, across wide rivers. The bridge built by Trajan across the Danube at Drobeta was dismantled by Hadrian to prevent easy
access to the Empire for hostile intruders; its piles were left in place and seemed to Dio, who had seen them, to show that there was nothing that could not be
accomplished by human ingenuity. Its designer, Apollodorus of Damascus (below, pp. 791 f.) who was responsible also for the Forum of Trajan, with its column
and library, was an architect of genius who would have been perfectly at ease in the company of Leonardo or Brunelleschi. He was certainly aware of his own
abilities; indeed, his contemptuous opinion of the architectural efforts of Hadrian, a gifted amateur, was believed to have led to his exile and execution by that
jealous man when he became Emperor.
The roads built by the Romans, originally for military purposes but in the nature of things quickly acquiring economic uses, linked together distant regions by direct
routes that were not matched until modern times, for it is not every society that has a frequent use for long-distance travel. Aerial views of the Roman roads of
Britain often show vividly the contrast between their direct, purposeful routes, professionally surveyed for long-distance communications, and the local lanes and
field-boundaries of medieval and early modern England which adjoin them, betraying the lines of an altogether more local economy.