This thesis aims to contribute to the on-going discussion in the field of architectural theory about public participation in the urban and architectural planning processes, as a practice of coproduction of spaces and societies. In an attempt to understand how the public is constructed in these processes and the role it may play, the thesis draws from the discussions in the field of Science and Technology in Society (STS) studies, particularly by scholars working with the actor-network theory (ANT). This research focuses on the controversy around the new Munch Museum in Bjørvika, Oslo - the so-called Lambda building - and its role in constructing “the public” in the planning process. Public buildings are usually a result of long deliberation processes that in their essence deal with envisioning and imaging the future public spaces. These processes involve an array of actors in the shape of decision-making bodies, architects, urban planners, and even materials. Yet it is “the building” and “the public” that are integral parts of planning and creating public buildings and spaces. What this thesis explores is who, what and how shapes “the public” in the case of the new Munch Museum. ANT scholars argue that technical and scientific objects have the capacity to become a “tool for democracy” and create a public around themselves by being associated with certain issues. Taking this as a starting point, the study examines how the object of Lambda – a building which exists in materialistic form only as images and textual descriptions of itself - brings about the emergence of “the public” in the process of planning for a new museum for Munch’s collection. The study traces the forming of the public in the controversy through the perspective of Lambda as a boundary object by looking at matters of concern that different actors in the process articulate. For each of the actors, Lambda represents a different reality. As a result, it is no longer only an architectural expression, but a multifaceted object whose agency in the process is visible through the different issues it evokes in the actors. The image of Lambda becomes thus in practice an ‘issuefied’ object - resonating with the different issues and concerns around which the public takes shape.