described as living systems. Living systems are constantly adapting, learning and evolving because their environment is always changing at different timescales. Living systems also require to be robust to endure unforeseen perturbations. Efficient cities have to do the same. It is not enough being “smart”. The demands and conditions of cities change constantly at different scales, so they must adapt, learn and evolve in a robust fashion in order to endure. Cities are not physically similar to living systems (no DNA, no membranes), but functionally, they should exhibit the same properties. From a materialist point of view, it makes no sense to speak about living cities. However, from a functionalist point of view, it is very relevant to speak about the relationships between living systems, artificial life, living technology, and urban systems. This is because the properties of living systems (natural or artificial) can be exploited to solve urban problems, making cities more adaptive and robust. If a notion of life based on entropy or information is used [1, 53], then one can even measure to what extent different cities can be considered to be alive, with a continuous transition between non-living and living systems [19]. In non-technical terms, if a city has a sufficient control over its own production, endowing it with a certain autonomy and integrity, then it can be usefully described as a living system. Living technology has been contributing to the increase of the “liveness” of cities, as it was shown by the examples presented in this paper. Moreover, the study of “living cities” is related to at least one of the open problems in artificial life [18]: To determine whether fundamentally novel living organizations can exist. Technology has always evolved [84], but with the aid of humans for most of its history. As living technology is developed, technology will be able not only to be more adaptive and robust, but to evolve by itself in directions that we cannot foresee. What can be said is that the integration between technology and living systems—including humans—will increase. Living cities will be the outcome of this integration. Will solutions to urban problems using living technology bring new problems? Since predictability is limited, most probably new problems will arise. Nevertheless, we can always 26