Digital twins of cities can assist policy makers during this process, providing an integral view on e.g. traffic intensities, air quality and noise. Furthermore, a digital twin enables policy makers to simulate ‘what if scenarios’ in a scenario-based analysis. Digital twins connect data, analytics and visualizations, which requires a system which integrates all these aspects in a single framework. This paper presents the Inter Model Broker framework, which is a scalable framework based on which large-scale digital twins can be built. A key property of our framework is that all connected system modules hold the relevant data locally in memory, which means that no central database is required.