This research analyses the impact of urban design on the vitality of public space. For the above, it explores the experience of inhabitants throughout indicators. This analysis allows us to identify relations between urban design and the perception of people inhabiting the place; identifying elements that favour or diminish the vitality of urban public spaces. As a case study, the Biobio Riverside Park, in Concepción, Chile, was selected. Based on its condition of being an attractive project, well located and designed; however, absent from activities and appropriation. The article researches bibliographically about some aspects of urban design, which modify the perception of inhabitants concerning the urban environment. Subsequently, several authors are analysed to identify the main urban design criteria considered for the development of an appropriate public space. With this background a methodological tool is constructed, to evaluate the perception of the inhabitants in relation to various urban design factors. Its application is done through surveys and planimetric analysis in the field. Finally, the survey and planimetry data were analysed simultaneously, in order to recognize the main elements of urban design, conditioning the vitality of the riverside park. Among the main results, security, accessibility, and diversity of activities emerge as the most influential urban design factors in the vitality of public space. Simultaneously, a clear difference between the participants' perception is identified, depending on the proximity of their residence to the case study. This implies that both the sense of appropriation, as well as the sense of security and the attractiveness of the urban landscape, are determining aspects of perception, to promote the vitality of public space.