For Korbach’s town hall, the planning team implemented an Urban Mining concept that spans from reusing the concrete from the existing building to designing the new replacement building as a storehouse of reusable material. The Urban Mining Index was applied for the first time to evaluate circularity. In the old quarter of Korbach in northern Hesse, the historic town hall from 1377 occupies a prominent position. A brutalist extension without a sense of scale was added in the early 1970s and subsequently dominated the urban surroundings. Since the annex also had numerous deficiencies in construction, function and energy efficiency, Korbach’s municipal government decided a redesign was needed.