This paper proposes that the organization of crafts may be a key catalyst in the emergence of urban communities. This is argued through a reassessment of finds from a non-ferrous metal workshop from the eighth century excavated in Ribe, Denmark. We analyse 3D laser scans in order to classify previously unidentified mould fragments, which show that the workshop produced a range of metal parts for composite products like wooden chests, belts and horse harnesses. Such production required an operational network, or réseau opératoire, to combine the necessary skills and expertise of several artisanal specializations. The need for collaboration between specialized craftspeople would have been a decisive incentive for the formation of permanent communities of an urban character. These observations point to a neglected bottom-up driver for the development of early urbanization.