This work is based on the belief that sustainability and resources management problems are not only referred to ecological systems, but are strictly linked with human activities, and concern socio -ecological systems of cities as a whole. Therefore, the study addresses the question of the balance between people and environment. Cities resilience depends on the stability of this balance in its projection in time, assuming the concept of resilience not just as the ability of the system to maintain a stable equilibrium condition, but, according with "resilient thinking" theories, as the ability to generate new stability landscapes that keep similar performances, identity and structure. This research investigates socio-ecological urban systems resilience, and it focuses on urban environment and specifically on city public spaces. The base hypothesis is that resilience of urban systems as a whole it is mainly determined by the balance of his social substratum, and that this is possible through a combination of strength and fragility in urban development. Public domain is the base structure of the city, where it comes, and it develops over time, the sense of citizenship on which depends the cooperation between people and its balance with environment. Hence, this is the field where this study investigates the concepts of persistence and change, and where it identifies stability frames and adapting elements. The first goal of this study is to demonstrate the relevance of public domain in keeping general resilience of the city. Then, it will investigate how public spaces could be designed based on the balance of persistence and change, which are the frames in public spaces that shouldn't change over time, to keep urban quality and collective identity, and, conversely, which elements should adapt to absorb stresses and to ensure general resilience. This will be verified through the comparison of recent studies and case studies, and a design of the author.