Collaboration and decision-making of humans usually entails logical reasoning that is expressed through discussions and individual arguments. Where collaborative work uses geo-spatial information and where decision-making has a spatial connotation, argumentation will include geographical references. Argumentation maps have been developed to support geographically referenced discussions and provide a visual access to debates in domains such as urban planning. The concept of argumentation maps provides for explicit links between arguments and the geographic objects they refer to. These geo-argumentative relations do not only allow for cartographic representation of arguments, but also support the querying of both, space and discussion. Combinations of spatial queries and retrieval of linked arguments provide a powerful way of analyzing and summarizing the current state of a debate. In this chapter, we provide an overview of the original argumentation model and we discuss related research and application development. We also link argumentation mapping to related concepts in geographic visualization, spatial decision support systems, and public participation GIS under the umbrella of collaborative GIS.