As a crucial sphere of activity for sustainable development, the urban district is moving more and more into the focus of planning and research. For several years there have been efforts in Karlsruhe Oststadt to fulfil the expectations of sustainable urban district development by working through and with a transdisciplinary real-world laboratory which consists of two projects: District Future – Urban Lab and Real-World Laboratory 131. The content of this combined real-world lab is related to an understanding of sustainable district development which includes not only social and participative aspects but also those concerning education and health. The aim of the real-world lab is to generate new knowledge and initiate new courses of action towards a sustainable district development. Starting points are the needs and the local knowledge of the citizens. The present article addresses the question which additional value a transdisciplinary real world-lab can provide for a future-oriented district development. To this end, a closer look is taken at the main characteristics of real-world laboratories in general and the activities of the sustainability experiment Social Affairs & Spaces in particular.