Cities are the vortex of matter and energy transformations that sustain the human condition in the twenty-first century. Many studies have shown that human societies are transforming urban phenomena at an impressive rate, even questioning the use of the rural–urban opposition nowadays [1]. Many architects and planners are referring to the “urban age” [2] to define the current time, as well as geologists and other scientists use the term “Anthropocene” [3] to refer to the geological epoch in which we are living. The term “Urbanocene” has also been proposed as the most appropriate for this epoch [46].

Cities are, by definition, the places where humans develop most of their activities; consequently, cities have been regarded as dissipative structures [7,8]: complex systems that increase internal organization by using continuous fluxes of information, matter, and energy. As a result, cities also increase entropy release to the environment, in the form of heat, emitted to the sky and dispersed in the air, soil, and water (Fig. 1). As a result of this process, urban areas have developed their own climate performance [9]. The thermodynamics of cities results are so important to understand the actual urbanization processes, as well as the same history of urbanization [10,11]. Energetic impact of land use changes, urban climates, and global warming has been estimated to be extremely high for the second half of the twenty-first century [12], with global energy penalties for many cities in the range of 1–20 kWh/m2year °C [13]. Moreover, global climate change impacts will be even more intense in cities than in the surroundings [14], and actual policies and technical regulations for the building sector will probably not be adequate for future climatic conditions [15,16].

Fig. 1
Change in Land Surface Temperature, 2017–2020, Concepción, Chile. Image Credits: Damaris Fredes, Camila Maturana and Joan Rojas, Fondecyt Project 1200275
Fig. 1
Change in Land Surface Temperature, 2017–2020, Concepción, Chile. Image Credits: Damaris Fredes, Camila Maturana and Joan Rojas, Fondecyt Project 1200275
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With respect to our healthy living, cities are involved in many processes that affect human physiology and psychology: from noise production to air pollution and urban heat islands. Since the pioneer studies of Howard, the climate of cities has been considered as one of the vectors of discomfort and risk of human health [17,18]. At the same time, cities provide a lot of opportunities, as recognized by many authors [19] and demonstrated by the fact that people are continuously moving to bigger metropolises, especially in developing countries [20].

Due to the importance of cities for our existence, sustainability of the urban environment has been the focus of research in urban studies during the past decades. This importance grows when we observe that urban growth is related to the increase in GDP [21,22]. More recently, COVID-19 pandemic also showed our fragility and exposition to viruses that now can change hosts in an easier way, thanks to the population density and the journey facilities offered by our times. For all exposed reasons, cities should deeply transform to survive and to follow offering a safe place for humanity. The transformation will include, of course, the inclusion of Nature-Based Solutions in buildings and urban infrastructure, but also a change in the pace of life is needed, as envisioned by unitary urbanism still in the 1970s [23,24]. New and existing cities, especially in developing countries, need safe public spaces, accessible and affordable for all, with the inclusion of green and blue infrastructure, public transport, and service buildings for art and culture [25]. Fluxes of any kind should be reduced, closing the loops as much as possible, to achieve a “low entropy city” (Fig. 2).

Fig. 2
High and low entropy cities. Credits: Butera and Palme 2021, reproduced with permission
Fig. 2
High and low entropy cities. Credits: Butera and Palme 2021, reproduced with permission
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This Special Issue, following the discussion opened during the Passive and Low Energy Architecture Conference “Will Cities Survive?” held in Santiago de Chile in November 2022, focuses on research topics related to urban sustainability, urban climate, green infrastructure, nature-based solutions, buildings adaptation for future climate, urban energy policies, informal settlements, and outdoor comfort. Contributions articulate these topics through technological developments, social studies for developing countries, megacities, and future adaptation of passive and active strategies to keep buildings and cities inside the planetary boundaries [26]. All these aspects linked to sustainable architecture and urban planning for current and future more sustainable cities are linked to each other. The closing of the energy and material cycles that we speak of requires the interrelation of these aspects and others in the planning of the city and buildings, especially in these times of climate change.

Ghosh et al. [27] ask how to adapt cities to climate change by using dynamic system analysis. Ganem et al. [28] reformulate passive strategies for buildings to adapt to new weather conditions. Sharp [29] proposes new methods to obtain weather data to be used in ambient conditioning. D’Amanzo et al. [30] look at office buildings' performance in high solar radiation environments, while Krarti et al. [31] present smart overhangs used for the climates of France. Biswajit [32] investigated the impact on productivity of extreme heat in Asian megacities. Kumar [33] focuses on heat exchangers for geothermal heat pumps. Finally, Schroeder [34] discusses the benefits of public space production by inhabitants in Piura, Perù. All points of view presented here, highly contribute to enhance the academic discussion on the future of architecture and urbanism, to force all of us to move forward, searching for the changes needed to respond to the great challenges to face in the next decades.

Conflict of Interest

There are no conflicts of interest.

Data Availability Statement

The data sets generated and supporting the findings of this article are obtainable from the corresponding author upon reasonable request.

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