By the early-to-mid-1st century AD, the growth of the Empire saw the establishment of glass working sites at locations along trade routes, with Cologne and other Rhineland centres becoming important glass working sites from the Imperial period,[1] and Syrian glass being exported as far as Italy.[20] During this period vessel forms varied between workshops, with areas such as the Rhineland and northern France producing distinctive forms which are not seen further south.[7] Growth in the industry continued into the 3rd century AD, when sites at the Colonia Claudia Agrippinensis appear to have experienced significant expansion,[21] and by the 3rd and early 4th centuries producers north of the Alps were exporting down to the north of Italy and the transalpine regions.[20]