Whether it’s fracking for shale gas, drilling for geothermal power, or disposing of radioactive waste, human intervention into the geological subsurface lies at the heart of many pressing environmental and social concerns. The trouble is, for most people, ‘the land below ground’ is an unfamiliar terrain – often either an unknowable alien underworld or an inviolable pristine frontier. Out of sight but very much in mind, the subterranean realm presents a new and challenging science/society interface. Addressing societal concerns rooted in the subsurface will require a cultural shift to re-connect individuals, communities and societies with what lies below and make public our scientific grasp of what goes on down there. Indeed, with the societal drive towards a sustainable future putting ever greater demands on the global underground, the long-term stewardship of our hidden common will be a critical scientific challenge for the coming decades.