We present the results of a study performed in Barcelona’s metropolitan area, aiming to examine the types, features and properties of different urban spaces subjectively experienced as dangerous by 70 city-dwellers (graduate students). Following a qualitative-descriptive methodological approach, the 125 places chosen by the subjects were described and assessed through photographs and previously structured self-reports, in terms of their physical and social cues - environmental ‘affordances’ (Gibson, 1977) - directly linked to feelings of fear and danger. The lack of lighting and of controllable exits, physical degradation (e.g. litter or broken furniture), and most importantly, the anticipation of potential offenders, the perception of isolation and the knowledge of experiences suffered by third persons, appear to be key components of localized danger. Theoretically, the study deepens in the social-psychological construction of the spatiality of danger, highlighting the role of meanings in its maintenance and transformation. The final aim of the research is to enrich the field of applied interventions that involve the design of comfortable and socially attachable urban environments.