Canary Wharf Underground Station, Canary Wharf, Docklands, London, England, United Kingdom, Europe

Rudolf Mine in Salina Turda salt mine in Turda city, Romania, Europe

People in an underground walkway, Beijing, China

Stairs in tunnel under houses, Pitigliano, Province Grosseto, southern Tuscany, Italy, Europe

Artwork in the Underground City walkway system, Underground City, Montréal, Quebec Province, Canada, North America

Artwork in the Underground City walkway system, Underground City, Montréal, Quebec Province, Canada, North America

Artwork in the Underground City walkway system, Underground City, Montréal, Quebec Province, Canada, North America

Artwork in the Underground City walkway system, Underground City, Montréal, Quebec Province, Canada, North America

Artwork in the Underground City walkway system, Underground City, Montréal, Quebec Province, Canada, North America

People walking in a pedestrian tunnel, Underground City walkway system, Underground City, Montréal, Quebec Province, Canada, North America

Silhouette of the man in underground tunnel

Empty stairs in underground tunnel

Empty stairs in underground tunnel

Illuminated pedestrian tunnel, walkway in the underground city of Montreal, Quebec, Canada, North America

Underground Metro System, Hong Kong, China