A proposed development by the City of London, at London Wall West, illustrates the intractable problems that can occur for a city seeking post-pandemic renewal whilst, at the same time, aiming to lead the way towards constructing a sustainable future. Current forecasts by the United Nations paint a gloomy picture of progress so far in meeting defined targets for combating climate change, with particular stress laid on the failure of cities to address their huge toll in generating CO₂ and Greenhouse Gas emissions. The way city policy makers of East Asia already have engaged with virtual reality, as an 'all or nothing' approach to digital transformation, offers a glimpse of how to proceed elsewhere—although, a similar policy, if applied in the West, will require that we adopt a 50/50 approach, partially physical, partly virtual, where people have choice on how much time they spend as an avatar in a metaverse. Success in developing an ecosystem of metaverses will depend on designers adopting a behavioral approach to constructing the virtual world; lessons from the past teach us that, as in the physical world, people's well-being in the metaverse will demand that we pay close attention to their environmental and psychological needs to ensure that a virtual life can be as fulfilling as life outside in the physical world. If all this can be achieved technologically, the resulting lifestyle changes, together with a requirement for less physical construction, give promise that we can get back on track in meeting the Paris Agreement target. By encompassing a radical policy of 'Building Less is More', cities, worldwide, will find a new route to zero carbon.