Founded in Wolfenbüttel in 1572, the Herzog August Library, often hailed as the world’s eighth wonder, is today an internationally acclaimed research library with over one million books and a vast collection of medieval manuscripts. It plans to add a new service building to enhance the historic ensemble that includes the Biblioteca Augusta main library building, the Direktorenhaus administration building, and the Magazin for closed stacks, collectively forming the Zentrum Altes Buch (Center for Old Books). In 2020, the Braunschweig State Building Management launched a competition for this expansion, in which our design earned the 3rd place. Our proposal inserts a new three-story building with a square footprint into the gap formed by the existing buildings, responding to the axiality and symmetry of the surrounding structures and pathways. A low, barrier-free base with ramp access provides flood protection and flexible landscaping. Two slim bridges create direct connections from the service building to both the main library and the Magazin.