Intervention is typical to semiosis in general, and it is also a specific form of action establishing its reality and significance and having consequences. The focus here is concerned with interventions into semiotic space, more specifically, with the semiotic space of the city. The semiotic space of the city is multi-layered and polyphonic, ranging from cultural models to sociocultural practices and umwelts of various organisms and their connections. Applying chronotopical analysis, developed initially in literary and cultural analysis, to the semiotic space of the city makes it possible to study the manifold of its relations, processes, layers and perspectives. However, it can remain a relatively static description of complexity and its processes – without acknowledging the agency in it. The agency and the orientation toward change are central to the concept of intervention. While interventions commonly rely on subjectively defined reality and respectively modelled actions and remain monological, there are also endeavours of more dialogical interventions. These include some practices of artistic, participative as well as ecological projects. The aim here is to specify conditions for and describability of dialogical interventions in the semiotic space of the city and outline their realisation and limitations. Comparison of examples from re-naming, rebranding, monuments and campaigns against them, re-design of urban squares, and landscape architecture experiments helps to outline dialogical approaches in the field of interventions.