In this poster I compare two types of visualization that can be distinguished by the role of the viewer. In the first, which I call “closed visualization,” interpretation is seen as a decoding of meanings already set by the author. The other—“open visualization”—sees the viewer as an active co-creator of meanings. In its processual character, open visualization elicits the critical potential of the imagination and is open to new contexts and interpretations. As such, open visualization democratizes the production of knowledge by enabling the critical analysis of the spectator. Instead of the hegemonic production of discourse typical of closed visualization, it introduces a “diagonal perspectivism” that allows problems to be seen from differentiated perspectives. As examples of the mentioned models of visualization I will analyze two projects: Neil Halloran’s The Shadow Peace: The Nuclear Threat and Aby Warburg’s Mnemosyne Atlas.