The City of Vienna has committed itself to the concept of Open Government Data – an open and transparent system that makes city data available to the public for their further use. The city administration has thus decided to its open data records to the population, businesses and the scientific community. Relevant data range from statistics and geographic data or traffic and transport to economic figures. Personal data are strictly excluded from the Open Data concept. The main prerequisite for data to be included is their machine readability in open formats. Open and freely accessible data allow for a broad and democratic exchange of knowledge, thus facilitating the dialogue between local citizens and the administrative authority. At the open data improve participation and communication, and are therefore conducive to innovation and development.