Life Between Buildings is a 1971 book by the Danish architect Jan Gehl arguing that the quality of a city should be judged by the optional, social outdoor activities its spaces support, not by its buildings or traffic capacity. Drawing on careful observation of how people actually use streets and squares, Gehl distinguished necessary, optional and social activities and showed that good public space draws out the latter two. The work grew from studies he and Ingrid Gehl made of Italian piazzas and Copenhagen's pedestrianised Strøget, contrasting human-scaled places with modernist plazas left empty. Its method was empirical counting and mapping of people on foot.
It supplied the evidence base and vocabulary for the global livable-streets, pedestrianisation and public-space movements, shaping interventions from Copenhagen to New York's Times Square. By prioritising walking and lingering over car flow, it shifted urban design toward people-centred measures of success.