The paper is a contribution to the analysis of the role and nature of the built environment in mind museums – former asylums turned into museums. It notably focuses on the adaptive reuse intervention implied in the design of these museums by revolving around the concept of atmosphere. By building on the case of the Museum of the History of Psychiatry in Reggio Emilia (IT) the paper examines how the peculiar atmosphere of the museum premise has been in play and worked out in the museum design. In doing so, it posits atmosphere as a designerly element alike other material and immaterial ones characterising the site and points out how such a perspective can provide a fruitful position for delving into the role of design in the overall project of a mind museum.