The 21 Century is the urban century with humans the dominant force shaping the planet’s future. This paper outlines why the era’s pressing imperatives need transformations in our production and habitation systems. These transformations require ecological design and technical and social innovations for adaptation. These adaptations need new visions of the city as nature and redefining the nature of the city. The paper begins by articulating the concept that all modern cities are forming a single global megacity – named Anthropocencia - linked together by gargantuan flows of information, goods and people. This megacity satisfies its rapacious appetites by drawing resources from a vast global hinterland. But the city is also a place of cultural production where the ferment of new ideas engenders the social and technological innovations needed for adapting to changing circumstances. Thousands of climate responsive and biophilic communities are in active exploration, ushering in transformations, utilising multiple strategies for re-naturing the city and its degraded hinterlands. Influential beyond traditional urban boundaries, cities are evolving assemblages of intertwined cultural, material and ecological elements, spawning novel ecosystems in and beyond urban areas. These ‘new natures’ are human created in at least four ways. Firstly, all conceptualisations of nature are cultural constructs. Secondly, urban natures exist within the constructed, materially and socially complex systems that are inherently politicised environments. Thirdly, new combinations of biotic and non-biotic elements are forming. Finally, with the Anthropocene simplistic definitional boundaries of ‘human’ or ‘natural’ are breaking down. This paper argues that new logics based on recognising the novel co-produced nature of ecosystems can be the basis of the new visions of the city as nature that will drive the forward-looking planning objectives that are needed to support transformations. These socialised objectives may be more useful than attempts to derive goals based on idealised past ‘natural’ states.