and adjusting city plans and infrastructure to encourage dense, complete, overall communities. A manifesto published in Barcelona in April 2020 proposed radical change in the organization of cities in the wake of COVID-19, and was signed by 160 academics and 300 architects. The proposal has four key elements: reorganization of mobility, (re) naturalization of the city, de-commodification of housing, and de-growth. Research models The 15-minute city is a proposal for developing a polycentric city, where density is made pleasant, one's proximity is vibrant, and social intensity (a large number of productive, intricately linked social ties) is real. The key element of the model has been described by Carlos Moreno as "chrono-urbanism" or a refocus of interest on time value rather than time cost. Moreno and the 15-minute city Moreno's 2021 article introduced the 15-minute city concept as a way to ensure that urban residents can fulfill six essential functions within a 15-minute walk or bike from their dwellings: living, working, commerce, healthcare, education and entertainment. The framework of this model has four components; density, proximity, diversity and digitalization. Moreno cites the work of Nikos Salingaros, who theorizes that an optimal density for urban development exists which would encourage local solutions to local problems. The authors discuss proximity in terms of both space and time, arguing that a 15-minute city would reduce the space and time necessary for activity. Diversity in this 15-minute city model refers to mixed-use development and multicultural neighborhoods, both of which Moreno and others argue would improve the urban experience and boost community participation in the planning process. Digitalization is a key aspect of the 15-minute city derived from smart cities. Moreno and others argue that a Fourth Industrial Revolution has reduced the need for commuting because of access to technology like virtual communication and online shopping. They conclude by stating that these four components, when implemented at scale, would form an accessible city with a high quality of life. Larson and the 20-minute city Kent Larson described the concept of a 20-minute city in a 2012 TED talk and his City Science Group at the MIT Media Lab has developed a neighborhood simulation platform to integrate the necessary design, technology, and policy interventions into "compact urban cells". In his "On Cities" masterclass for the Norman Foster Foundation, Larson proposed that the planet is becoming a network of cities, and that successful cities in the future will