Perceived as a complex system, public space could be examined through the means of complexity thinking. Complexity thinking not only offers a new urban terminology delivering interesting insights on the city and its public space, it also offers new tools that could deepen our understanding of their major issues. In this paper, the complex case of Horsh Beirut is diagnosed with one of these tools: Systemic Triangulation. As a trans disciplinary tool for relational diagnosis, Systemic Triangulation acknowledges the inscription of urban problems in structural, functional and dynamic continuums, establishing the relationships between them, and projecting interactions between the system and its environment. This paper searches for the implication of this method, based on non-linear representations of urban reality, in public space design and management. And explores to what extent the systemic approach could give us fresh answers on classic urban problems such as dysfunctional green public spaces and spatial segregation.