Sustainable Development: A Challenge for All Humankind" - was the title of an event held on 7 November 2023 to celebrate the 85th birthday and achievements of Prof. Dr Klaus Töpfer. The event was organised by the Konrad Adenauer Foundation, the Research Institute for Sustainability - Helmholtz Centre Potsdam (RIFS - formerly IASS) and the foundation Stiftung Zukunftsfähigkeit, which is affiliated with the NGO Germanwatch. In this report, Klaus Milke, Chair of the Board of Stiftung Zukunftsfähigkeit, shares his impressions of the evening.