Cities tend to be built in areas of high biodiversity, and the accelerating pace of urbanization threatens the persistence of many species and ecological communities globally. However, urban environments also offer unique prospects for biological conservation, with multiple benefits for humans and other species. We present seven ecological principles to conserve and increase the biodiversity of cities, using metaphors to bridge the gap between the languages of built-environment and conservation professionals. We draw upon John Ruskin's famous essay on the seven lamps of architecture, but more generally on the thinking of built-environment pioneers such as Patrick Geddes (1854–1932) who proposed a synoptic view of the urban environment that included humans and non-humans alike. To explain each principle or ‘lamp’ of urban biodiversity, we use an understanding from the built-environment disciplines as a base and demonstrate through metaphor that planning for the more-than-human does not require a conceptual leap. We conclude our discussion with ten practical strategies for turning on these lamps in cities. Urban planners, architects, landscape architects, engineers and other built-environmental professionals have a key role to play in a paradigm shift to plan for the more-than-human, because of their direct influence on the evolving urban environment. This essay is intended to increase dialogue between ecologists and members of these professions, and thus increase the biodiversity of cities around the world.