The virtual digital twin of the city of Hannover maps the environment in real time and foresees changes in state through learning algorithms. The data platform can be used in many ways in the future: for example, for the highly accurate operation of autonomous vehicles or for the localization and tracking of goods. The platform can support navigation in buildings, optimize production processes, visualize planning, or even be helpful in reserving parking spaces for sales booths or moving trucks. Tourist offers such as adventure tours through historic Hanover or the Herrenhäuser Gardens are conceivable. Citizens, companies, logistics providers, transport service providers, planning offices, the city administration, and even security forces such as the fire department are all expected to benefit. The range of applications for the idea is almost endless. Some use cases – when it comes to controlling a machine, for example – require only three-dimensional coordinates and data on the current state of the environment. Other applications extend the perception of reality by adding digital images in a location-based manner and superimposing them on reality. This so-called augmented reality then requires a smartphone, tablet or corresponding glasses. The digital twin is to be openly accessible and provide interfaces for developers from the start-up scene, for established companies and for research.