People walking from one part of the city to another through London’s railway arches leave traces on their paths. These traces can be observed in objects, posters or graffiti imprinted onto the robust fabric. What happens if a shop moves out and the space left underneath the arch is kept vacant? What if a light bulb was forgotten by the former shop owner, or a wooden shelf? While plaster crumbles and falls to the ground, advertisement posters are hung up against crude brick walls. A beverage dispenser might be added, or a graffiti showing an iconic figure is sprayed onto the newly painted wall by youngsters from the neighbourhood. Within this movement, the passageways underneath the railway act as bottlenecks, infrastructural junctions where city life steadily leaves its traces.