Media architecture has emerged as a relevant field of study within HCI since its inception at the turn of the century. While media architecture has the potential to radically affect the social space into which it is introduced, much research in the field was initially carried out through experimental installations in public spaces, often with higher emphasis on examining the properties of this novel type of interface, rather than examining the impact it had on the social context. In this paper, we look back at the field and analyze interactive urban media architecture covering a period of fifteen years of practice with a particular emphasis on how installations have influenced modes and patterns of social behaviour. We classify nine representative installations according to their physical layout, interaction strategies and types of interface. We focus on how these installations were perceived and used by their respective audiences and outline six modes of social interaction that unfold with these installations. From this analysis, we derive seven social interaction patterns, which represent different strategies for designing and employing media architecture to influence social interaction.