Don't hold your breath to see one of these in the U.S.
The "iceberg" metaphor made literal.
Slow commute? No problem.
Researchers are creating the first 3-D map of the city's hundreds of manmade caverns.
Transit officials say a pilot program has helped reduce garbage inside stations, but results elsewhere have been mixed.
Researchers are using rider data to better understand how stressed subway crowds flow through the system.
70 sectarians are found living in an underground bunker in Russia.
Artist Stephen Walter maps the city below the surface.
The Foursquare-style Chromaroma program tracks London Tube riders wherever they go