The wide range of benefits and impacts on citizens generated by Smart Cities via the advancements of  Cloud Computing and the Internet of Things (IoT) affect critical aspects in the growth of urban areas and electronic government services, preserving and promoting historical heritage, entertainment, public safety, energy saving and use of renewable energy, garbage collection and recycling, traffic control, public lighting, irrigation of green areas, care for the environment and the resilience of the city. Open innovation offers a way to respond to the critical requirements of a city with the involvement of experts and the population in general, developing and making use of Open Data, Big Data, sensors, drones, Machine Learning, and Augmented Reality technologies, among others, that promise to face the challenges of the cities of the future.