Anja Rosen is an expert in urban mining. She uses the city as a raw material mine. In her lecture, the founder of C5 and Professor of Circular Construction at the Münster School of Architecture presents innovative urban mining projects that she has accompanied in planning. In doing so, she measures and optimizes circular material use with the Urban Mining Index, which she developed during her doctorate at the University of Wuppertal. This makes it clear in black and white: preserving and reusing is better than recycling. But which hurdles need to be overcome for this, and how can this be achieved in a nation of standardization world champions?