Peripheral and suburban urban areas though hosting major urban dynamics and population groups, are often perceived negatively, and have not received the attention of current urban planning and design practices in steering the necessary regeneration. In Portugal, as in other countries, urban development reflects these problems. In research, policy and practice, public space (PS) is addressed as a means to attain a better urban environment within sustainable development, but it also reflects inequalities in its provision and distribution, especially in more extensive and diversified urban contexts. While the recent crises have showcased the importance and potential of PS, they also stressed the urge for these places to be transformed. The main purpose of this project is to understand where and how to redesign PS to deal with transition challenges. The research does this by understanding and reframing the way PS is addressed in the “extensive city” and by discussing with stakeholders its value and potential to contribute to a more sustainable transition path. Through a critical analysis of the public space of peripheral areas in the Lisbon metropolis, the research aims to achieve prospective reasoning to tackle urban change obstacles. Partial goals include: mapping and characterising these public spaces; locating the main challenges and opportunities to be tackled; giving visibility to peripheral urban areas forwarding policy guidelines.