Cologne embraces a revolutionary moment happening in the building and construction industry with the ReBAU project, which has set its sights not only on energy efficiency but spearheading comprehensive resource and climate protection measures. ReBAU marks a departure from traditional energy-saving approaches as it pivots towards holistic resources and climate protection in construction. Shifting the focus from the operational phase to the entire lifespan of a building, the project employs renewable resources efficiently, which embrace the principles of the Circular Economy. This shift not only reduces greenhouse gas emissions but also minimizes raw material consumption and primary energy usage, which overall contributes significantly to a transformative building culture. At the heart of the ReBAU initiative is the establishment of a center for regional resource transition in the built environment. This collaborative platform involves businesses, public authorities, research institutions and civil organizations, which will then consolidate resources to start new educational activities. The project unfolds through various pilot initiatives such as the development of circular mineral building products, prototyping a Circular Economy-inspired neighborhood, innovation calls for groundbreaking construction methods and a secondary raw material exchange platform. ReBAU mobilizes previously overlooked potentials for cost-neutral climate protection within the construction industry of North Rhine-Westphalia. The project aligns with the principles of resource efficiency and circularity, which aims to reshape the building and construction landscape into a more environmentally friendly region. In the evolution of the building sector, ReBAU introduces the concept of a resource transition as the third major transformation. Traditionally reliant on non-renewable resources and operating within a 'Take-Make-Dispose' system, the construction industry is now poised for a sustainable overhaul. ReBAU pioneers a circular approach, where materials are repurposed, creating a more resilient and eco-conscious building economy. As ReBAU charts new territories, Cologne positions itself as a hub for pioneering sustainable construction practices, setting a precedent for resource-conscious building cultures globally.