The dichotomy between ‘strong’ and ‘weak’ ties is a common theme in sociological scholarship dealing with urban space, yet urban ethnographers have long been describing the prevalence of impersonal relations. Such relations can be described as fleeting encounters between complete strangers, while others – as in the case of ‘nodding’ relationships – are durable and have yet to be conceptualised. The notion of ‘invisible ties’ is proposed as a conceptual handle for studying typical urban relations that complement the established notions of strong and weak ties. Through an empirical study of four residential buildings in Geneva (Switzerland), these ‘invisible ties’ are revealed by means of a systemic approach to social urban life, from which two key actors emerge: ‘socialisers’ and ‘figures’. This research addresses gaps in the literature on interpersonal relations in urban contexts by focusing on the interplay between different types of social ties, encompassing the whole continuum from anonymity to intimacy.