Citizen laboratories will shape the smart cities of the future. Smart cities need engaged citizens to help build and test new technologies through citizen-driven projects. Citilab in Cornellà de Llobregat, Spain is an example of a citizen laboratory, where over 5,000 members and 50 employees collaborate on projects around senior citizens, music, education, and job creation to test innovations and shape their city as an open living lab. These citizen laboratories allow residents to co-create their city infrastructure and new technologies through real-world experimentation and community engagement.