The large and wide-ranging photography collection of the Kunsthistorisches Institut of the Rheinische Friedrich-Wilhelms-Universität Bonn for a long time attracted very little scholarly attention. Only when plans to renovate its former premises in the Bonner Schloss were announced did the in-depth engagement with its historical holdings begin. The photographs are now being inventorized, digitalized and their provenance investigated as part of a research project. The collection comprises circa 100,000 black-and-white prints, around 5,000 glass slides, and parts of what was once a very large collection of small-format slides. Used for decades as a source of teaching and research materials, the collection reflects the history of the Bonn-based institute that houses it. Having retained its original cataloging system of 1952, it is also powerful testimony to the history of art history as a scholarly discipline.