Digital 3D models of cultural heritage have been used since the 1980s as a tool for research and knowledge transfer in various disciplines, such as archaeology, architecture and art history and museology. Such models are created through the retrodigitisation of existing heritage, or, on the other hand, through the interpretative reconstruction of historical objects that no longer exist. Although the working methods, data structures, and results of both approaches differ fundamentally, there are overarching requirements concerning visualising the 3D data contained and the accessibility of meta- and paradata sets. The second stage of the DFG-Viewer 3D - Infrastructure for digital 3D reconstructions endeavours to expand the structures, repositories and infrastructures established in the first project phase. We foresee the inclusion of further repositories and infrastructures in the DFG 3D Viewer and providing an executable reference installation. Further development comprises further work on the software architecture (requirements elicitation, use cases and the exchange format and mapping) and the technical components (testing and integrating the 3D viewer stack). Particular attention will be given to the interoperability of the components under development to be implemented four reference repositories (ThULB Jena, UB Heidelberg, Darmstadt, TIB Hannover) and the dissemination of the project to the German and European community with a view to further discussion towards the shaping of standards for the publication of digital 3D models of cultural heritage.