Today, a wide array of Internet of Things (IoT) devices are deployed to sense physical conditions and urban activities in cities. However, only some of the available IoT resources are used for decision-making. Interoperability on technical, semantic and organisational levels is crucial in unlocking the potential of using multiple IoT device networks and IoT device types to support decision-making and fuel the digital twin with relevant live data stored to generate time-series data to feed simulation models and allow predictive modelling. Standard communication protocols and robust infrastructures are vital for smooth IoT integration in an increasingly data driven governance. This chapter provides an overview of relevant standards for IoT that can be used in everything from dataspaces to simulation models. It describes interoperability requirements for different types of sensors, covering both professional high-fidelity IoT networks and community driven citizen science initiatives. Decision-makers can reap the benefits in the form of better insights and a more holistic policy impact assessment by leveraging new data sources and tools, such as digital twins, Augmented Reality (AR), and visualisation dashboards. Several case studies illustrate the possibilities of using IoT to create data driven solutions for cities and citizens.