Neon Subway sign, Times Square, Manhattan, New York City, United States of America, North America

Aerial image of entrance to The Channel Tunnel (Chunnel) (Eurotunnel), beneath the English Channel, Kent, England, United Kingdom, Europe

Signs of the Civil War in Sant Felip Neri Square, Gothic Quarter, Barcelona, Catalonia, Spain, Europe

Couple walking into the light, York tunnel, York, England, United Kingdom, Europe

Taksim Tunnel Tram at Tunnel Square, Istanbul, Turkey, Europe

Pool of Shiloh, Hezekiah's tunnel, Jerusalem, Israel, Middle East

Sound Transit Link Light Rail transit system, transit tunnel, Pioneer Square Station, Seattle, Washington, United States of America, USA