Future cities? A morphogenetic code idea is presented. We need a conceptually different idea of cities which paradigmatically shifts their forms and structures toward more liveable future environments, both for us and our planet. The Isobenefit Urbanism is conceived within a medium-long term perspective mixing a macro top-down planning with a micro bottom-up spontaneous evolution in an attempt to moderate the human forces which typically induce agglomeration benefits and costs, maintaining the former while limiting the latter. It indicates a simple urban morphogenetic code to generate cities that are walkable, carless, low carbon, connected, compact, multifunctional settlements throughout nature, with unplanned forms and dinamically unlimitedly changeable/extendable, in which one can feel both urbanity and nature. By holding constant the number of inhabitants of a usual city/megacity, its Isobenefit city counterpart would enjoy the same (or greater) economies of scale benefits but without most of their costs. The Isobenefit Urbanism model might offer a potential solution to wild cementification, urban heat island effects, destruction of natural land and biodiversity, carbon emissions, congestion, air pollution, urbanicity and mental well-being, as well as provide a model to host the 3 billion new urban dwellers of the next few decades. Its ambition is to enjoy the economies of agglomeration without incurring to their diseconomies, manifested by sublinear and superlinear outputs scaling with city (population) size, typically infrastructural the former and socioeconomic the latter, without misusing lands and compromising daily rural/natural contacts.