The Smart Cities Symposium Prague 2017 (the third annual conference) aims at the exchange of ideas and best practices in the field of Smart cities. It covers the whole range of topics, from the system point of view, through data mining and data processing, smart grids, up to multi-agent systems and other soft computing approaches. The objective of this conference is to define the future applications for the field of smart cities. The results should be based on the theoretical backgrounds, but aim on the usage of best practices for real-world applications.