This essay attempts to elaborate a notion of ‘public domain’ in order to capture the elusive features of ‘public-ness’. Its leading question can thus be put as follows: ‘what is specifically public in public situations and public spaces? What is the specific dynamic that contradistinguishes the public?’ A series of empirical cases taken from different contexts, which functions as thought-provoking illustration of the theoretical issues at stakes, is discussed. Theoretically, the essay draws from, and suggests a critical synthesis of, four major threads of research: political and social philosophy (notion of ‘public sphere’), interaction sociology and cultural studies (notion of ‘public realm’), urban studies (notion of ‘public space’) and the literature on governance and policing (notion of ‘public order’). Accordingly, the public domain is conceptualised as an ecology of three ecologies; in other words, it is regarded as composed of a media ecology (or, an ecology of mediations), an urban ecology and an ecology of attentions. An evental perspective on the public domain is proposed, which takes into account the convergences and the tensions that exist within the social between material and immaterial dimensions. From this perspective, the public domain is inherently defined by the events of visibility, accessibility, circulation, appropriation and resistance.