Future cities have to face several strongly interrelated key challenges like population growth, environmental problems, city wide facility and utility management, increasing consumption of resources as well as a changing society. To overcome these challenges new concepts of Smart Cities with sustainable economic growth, high environmental quality, high quality of life and sustainable management of resources are proposed. Future technologies like ICT combined with human- and social capital, new demographic structures and future oriented city management are the key instrument to realize the vision of Smart Cities. Technological, regulatory as well as societal prerequisites are required to achieve the goal of Smarter Cities. The technological prerequisites are mainly modern ICT to link various fields of actions in a Smart City. Furthermore, intelligent supply and sensor networks are necessary to optimize the infrastructure. To facilitate technological progress and advanced ICT as well as to provide information to decision makers and the population of the city an excellent data base is required. Regulatory prerequisites are regularizations, laws, standardizations, data security and privacy as well as clear definitions of visions and mission statements for urban development. Moreover, urban planning integrating transport and energy planning, a collaborative city administration as well as new management structures and business fields are necessary. The most important societal prerequisite of a Smart City is the support of a smart urban population (Smart Citizens), which is capable of making decisions and taking responsibility for the city development. Hence, necessary societal requirements are democratic participation, education, information (taking needs of diverse social groups into account), subsidies, incentives, but overall raising awareness.