CitySDK is creating a toolkit for the development of digital services within cities. The toolkit comprises of open and interoperable digital service interfaces as well as processes, guidelines and usability standards. CitySDK enables a more efficient utilisation of the expertise and know-how of developer communities to be applied in city service development. The Project focuses on three Pilot domains: Smart Participation, Smart Mobility and Smart Tourism. This talk will present the state of the art in Open Source Linked Data applications, taking the Smart Mobility API as the use-cae. It will discuss preliminary results and invite participants to join the ecosystem.