Simulation-based assessments are a cost- and time-effective way of evaluating various aspects of large energy systems. For instance, they can help in the design process of energy systems, where they provide insights into technical or economic questions. Or they can be used for developing operational strategies and controllers to increase the efficiency of energy systems. In the case of integrated urban energy systems, simulation-based assessments still remain challenging due to their complex requirements, from both a methodological as well as a technical perspective. This is not only due to the size of the considered systems but also due to the fact that they comprise and integrate subsystems that are related to different engineering domains (e.g., electric grids and heat networks) and different stakeholders. Nevertheless, recent work has demonstrated how innovative simulation approaches can be successfully utilized in this context, enabling detailed multi-domain assessments for urban energy systems. However, not only models and tools are necessary for such complex simulation based assessments. Issues related to data availability and reproducibility are of equal importance, in order to set up simulations and compare results. And, with the help of proper methodologies, it is possible to exploit synergies between complementary simulation approaches for holistic assessments. Within this context, this paper highlights recent developments from research projects that target these issues. The examples demonstrate how these new approaches help in understanding the associated risks and potentials, paving the way for early adopters to implement innovative concepts in the context of integrated urban energy systems.@en