Where was the first subway in the world located ?

The oldest rapid transit system in the world is the London Underground, which opened in 1863. The two primary ways that subway tunnels are constructed are by cut and cover and tunnel boring. The world's most extensive urban rail systems are Tokyo's rail network and Osaka, Japan.

In the United Kingdom and some Commonwealth countries (such as Australia, Canada, Hong Kong, and Singapore), the term subway normally refers to a specially constructed underpass for pedestrians and/or cyclists beneath a road or railway, allowing them to reach the other side in safety.

The term is also used in the United States, specifically by the California Department of Transportation, for a road undercrossing which is depressed.

Underground pedestrian passageways are less common in North American cities than in European cities of comparable size. They are constructed when it is necessary for pedestrians to cross a railroad or a limited-access highway such as an interstate highway, and of course they appear at the exits from underground rapid transit systems, but one would be rarely built just to enable people to cross an ordinary city street. When they are built, the term "pedestrian underpass" is more likely to be used, since the word "subway" is usually used there to refer to rail-based rapid transit systems such as New York Subway.