In this essay, I intend to offer an alternative to viewing the museum and the exhibition through the visitor’s expectations. Instead, I shall follow all those actors whom the viewer usually does not meet in the museum: the artists, the curators, the technicians and the workers. The visitor knows they exist and that they have worked hard to stage all these art installations for the public, but he or she has never seen them working, discussing and acting together in the artistic process. This essay is an invitation to the viewer to follow these actors and to perform a slow and unusual visit to the exhibition Häuser, held in Musée d’art Moderne de la Ville de Paris in 1999. In this context, art objects will be seen in the process of their doing. A specific case will be discussed: the installation of a Volkswagen bus, model 1977, in the museum, and its transformation into a contemporary art installation named Mückenbus. This example is particularly interesting, because the bus passes though the museum entrance door, back and forth, as does a visitor, and because a whole group of actors is assembled and mobilized to help insert the bus and to adjust its position in the exhibition hall. I will describe how artists, curators, technicians and workers adapt space, tools and materials to the artistic idea; what happens to the bus when it meets the museum, and consider some of the ways in which such installation operations transform the museum world in the process. Before analyzing the bus’s tribulations, however, I will trace briefly some key research tendencies on museums that help us to consider this particular case.