The continued pressure to densify some of the world’s big cities brings with it upward pressure on land values. With outward expansion often not feasible due to sustainability or cost of distance reasons, the only way tends to be up. Or increasingly also down. Digging out underground space is costly and takes time (both not helpful in development appraisals); but as land values rise, so the viability of digging increases. The spaces below our cities are a natural home for infrastructure and utilities but are increasingly considered for a wider range of uses. In response, Singapore is preparing its first underground Masterplan and has restricted private land rights to the level of existing basements. These and similar plans could provide blueprints for the next wave of cities that seek to ameliorate some of the ills of the past. In particular, it feels unlikely that the deliberately planned city of the future will have any transport movements above ground. Underground homes will, however, hopefully, be a more distant prospect.