The contemporary city is rapidly changing, generating within itself and at the border new types of spaces. Among these spaces there are Terrain Vague or urban voids, undeveloped spaces within urban areas, at different scales, where emptiness prevails over fullness and naturalness prevails over built, with unclear thresholds. Even if underused, ambiguous, abandoned, these spaces are a precious resource of future challenges of the city with a great potential. Urban voids could play a key role in achieving a sustainable, resilient, inclusive development of cities. It is necessary to develop a new vision for these spaces based on a more flexible, dynamic, and reversible approach focused on bottom-up design, social equality, and nature-based solutions. In this context, it is urgent to map, to categorize urban voids of Lisbon, and to develop a framework to evaluate potential and new approaches, using digital interactive, computational and visualization tools, based on Data-Informed Design.