In the last decades, historic European cities such as Lisbon have faced the challenge of aging dwellings, infrastructures, and a growing number of vacant buildings. These vacant spaces represent both a problem and an opportunity for the cities. While they detract from the city’s aesthetics and safety, they also offer a chance for renewal. Strategic reuse can address housing shortages, boost businesses, and revitalize neighborhoods. This study examines Lisbon’s efforts to revitalize vacant buildings from 2009 to 2022, with projections extending into the next five to ten years. Analyzing data on building use and reoccupation, the study reveals significant progress. A detailed survey of 1674 vacant buildings in 2009 shows many have been transformed. Then, through a GIS-based analysis, the immediate social and economic impacts of the requalification process are assessed, and two future development scenarios are evaluated. By 2022, 60% of these buildings (999) were reoccupied, expanding housing options and driving economic growth. Shops saw a 166% increase in occupancy, highlighting a thriving commercial sector. Additionally, 27% of the reoccupied buildings now hold tourism activities, including short-rental accommodation and hotels. Short- and long-term scenarios are proposed based on a comprehensive survey that captured the status, function, and preservation conditions of the vacant buildings within the city. These scenarios are planning tools for exploring potential future trajectories of urban development, allowing policymakers to anticipate issues, mitigate risks, and make informed decisions, shaping a more sustainable and resilient Lisbon.