Digital twins are precise virtual models of real objects or systems, continuously fed with real-time data. In the public sector, they are gaining importance in areas such as urban planning, infrastructure management and disaster protection. A city's digital twin can simulate traffic flows, energy consumption or flood risks, enabling evidence-based decisions. Authorities use digital twins to plan infrastructure projects, identify maintenance needs early and deploy resources more efficiently. At the European level, the Destination Earth initiative promotes building a digital twin of the Earth for climate modelling. Data sovereignty, interoperability and the quality of underlying data are decisive success factors for governmental use of digital twins.