Nexthamburg is a citizen-based think tank in urban development of Hamburg. The independent and open crowd-sourcing project Nexthamburg gives citizens the possibility to contribute to current discussions about urban development in Hamburg with their own ideas. It gives them space to grow, for discussion, and a feedback from its community of more than 5.000 as well as from experts and the Nexthamburg team. Every participant can create own visions for Hamburg on www.nexthamburg.de, vote for other visions or ideas, and participate at events to learn about urban development, contribute with own ideas and discuss them with others, connect with other citizens, organizations, and representatives. Nexthamburg has developed different tools and formats for those events, such as the so-called idea speed dating. The long-term goal of the project is to organize a crowd-funding channel for promising ideas for Hamburg’s urban development to finance feasibility studies and realization efforts.