This article contributes to shedding light, documenting, and disseminating a pioneer event that has not been part of the recorded history of urban planning. In 1991, two feminist engineers working at the City of Vienna’s Urban Planning Office organized a ground-breaking exhibition with the aim of understanding gender bias in urban design. The event exceeded their prospects in an unanticipated way. Since 1991, the City of Vienna led the way to the conceptualization of gender mainstreaming that was happening at the European level – and that did not take place until 1997, when the Amsterdam Treaty came into effect. In 1992, the City of Vienna established the Women’s Office, with authority in urban affairs. Paradoxically, the success of the exhibition did not allow the organizers to properly document and preserve it, nor was it conserved in the City’s Archive. This unprecedented research relies on unreleased archival material gathered from the personal archives of the exhibition’s photographers, as well as from ad-hoc interviews with the organizers, Jutta Kleedorfer and Eva Kail. Thirty years later, the City of Vienna is known for this approach to urban planning. The exhibition ‘Who Owns Public Spaces? Women’s Everyday Life in the City’ was the turning point.