The dark and ominous warning that marks the threshold into Dante's underworld, as well as the preface to Karl Marx's philosophical tract Capital: A Critique of Political Economy, reveals the complex intersection of physical, metaphorical and metaphysical appropriations of underground space from antiquity to modernity. Classical themes of katabasis, or the meta-narrative of descent that dominated images of heroic journeys, articulated a poetics of the underground that embraced eschatological themes of death, redemption and renewal. Although these associations remained critical in apprehending the underground in earlier representations, it was not until the eighteenth century that scientific discourse of geological explorations infused the rhetoric with more rational and technical sensibilities, ultimately leading to such distinctions as the ‘organic’ and the ‘inorganic’ environment later defined by the urban critic Lewis Mumford. The space below ground, once unknowable and unseen, was readily available to the naked eye, and the contradictions between the concrete ‘place’ and the imagined ‘space’ created anxieties on the surface of modern life, especially as subterranean networks began to proliferate in the nineteenth century, most spectacularly in the cities of London and Paris.