Project management and innovation methods seem to have recently entered museums, which can no longer be described as organizations reluctant to innovation. However, existing literature on museum management tends to analyze these processes based on a particular representation of museum activity, in which design work is over or absent. This article identifies design activity within museums, especially in matter of collection and exhibition management. It builds on a design-space extension framework to model collection management and exhibition design processes. The empirical case of the Louvre-Lens design, based on a collaborative research methodology, shows how a large institution manage design space extension and forces exhibition designers to overcome traditional rule-based processes. Three main results are drawn from this case study at the Louvre. First, we show that museums have always been organized around a design strategy; second, we draw managerial implications on the extension of design spaces; finally, we map contemporary emerging museum activities and practices as design space extensions.