When considering the role of Augmented Reality (AR) in the urban space, most previous work is focusing on touristic and everyday life use cases. However, the project "Archäologie der Gegenwart" which we present in this paper illustrates the different aspects of change in Hamm during the last 50 years. Thus, our AR approach opens up a deeper understanding of the urban cultural change processes by the means of AR. Our considerations lead to adding an AR layer as a fifth social dimension in the

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... an space. Technically, we robustly link this fifth layer with the existing topography by marker-based tracking with six degrees of freedom (6 DOF). When building AR applications for the urban space, the deeper understanding of the marker paradigm is crucial: During our workshops we identified and analyzed seven requirements for the utilization of markers in the public urban space. Additionally, we analyzed the general AR marker paradigm from the human-computer interaction (HCI) perspective by considering the affordances and signifiers of the marker objects themselves, analyzing the tracking technology and summarizing the marker's role for past, present and future AR applications. Thus, the role of the AR marker is twofold: On the one hand the marker is part of the 6 DOF tracking technology, on the other hand it makes AR layers perceivable in the urban space. We expect that the importance of these markings for guiding citizens through AR experiences will emerge in urban spaces, whereas the role of markers for technical tracking purposes will decrease.