Smart Cities have been envisaged in recent years from a technological standpoint or from a social sciences perspective. In order to understand better what is at stake with their rise, this lecture will propose two additional approaches. The first will be historical. What can we learn about smart cities by placing their emergence within the broader framework of the evolution of the relations between cities, technologies and societies since the dawn of the industrial revolution? Smart cities could very well represent a new "paradigm", to use Thomas Kuhn's concept, which is about to replace the networked city inherited from the 19th century. A second approach will be in terms of design, for smart cities raise all kinds of challenges for engineers and architects in charge of the conception of infrastructures and buildings. There again, what is taking place looks like a drastic departure from an established conception of projects.