**Preface to "CITIES: Energetic Efficiency, Sustainability; Infrastructures, Energy and the Environment; Mobility and IoT; Governance and Citizenship"**

Cities are changing; this is a reality. As this change takes place, advances in research must propose solutions to the numerous problems that arise with it. Administration, universities, and companies must cooperate to establish the foundations of the Smart City.

In this sense, the main pillars of a city are:


Therefore, this SI will be focused on thse topics. Submissions of both original research and review articles are invited. Additionally, invited papers based on excellent contributions to the 2020 CIUDADES INTELIGENTES TOTALMENTE INTEGRALES, EFICIENTES Y SOSTENIBLES (CITIES) will be included. We hope that this collection of papers will serve as an inspiration for all those interested in the prosperity of smart cities. This book integrates scientific articles on energy, mobility, artificial intelligence and sensors. All of them are within the scope of smart cities.

**Luis Hern ´andez-Callejo, V´ıctor Alonso G ´omez, Sergio Nesmachnow, Vicente Leite, Javier Prieto, Angela Ferreira ˆ**

*Editors*
