 Examples of proto-civilisations are found preceding the development of almost all civilisations, but there are also examples of many proto-civilisations that failed to generate a separate civilisation.For example, the La Tene Celtic culture of "oppida", stretching from such sites as at Hueneburg in Southern Germany, to the Belgae kingdoms of Southern Britain, show many of the characteristics of a proto-civilisation; including the settlement hierarchy already mentioned, the development of an upper "princely" class having a monopoly on institutionalised violence, the development of specialised functionaries, artisans and craftspeople.It is quite possible that this development would have led to a fully Celtic civilisation, if the areas had not been conquered by the Romans and included as the western part of the Roman Empire.