Underground city

An underground city is a series of linked subterranean spaces that may provide a defensive refuge; a place for living, working or shopping; a transit system; mausolea; wine or storage cellars; cisterns or drainage channels; or several of these. The term may also refer to a network of tunnels that connects buildings beneath street level., which may house office blocks, shopping malls, metro stations, theatres, and other attractions. These passages can usually be accessed through the public space of any of the buildings connecting to them, and sometimes have separate entries as well. This latter definition encompasses many modern structures, whereas the former more generally covers tunnel systems from ancient times to the present day.

Underground cities are especially functional in cities with very cold or hot climates, because they permit activities to be comfortably accessible year round without regard to the weather. Underground cities are similar in nature to skyway systems and may include some buildings linked by skyways or above-ground corridors rather than underground.

Possibly the most famous underground cities are Montreal's RÉSO, used by more people than any other locale and the largest underground city network in the world, and Toronto's PATH, which according to Guinness World Records, is the largest underground shopping complex in the world with 371,600 square metres (3,999,869 sq ft) of retail space. Japan's underground networks, whereas individually smaller, are the most extensive overall with an estimated 76 underground shopping streets totaling over 900,000 square metres (9,687,519 sq ft) of floor space in 1996, with many expansions since then.

Countries with underground cities are listed below.

Buenos Aires, capital of Argentina, has an extensive amount of underground cities in its Subte (the oldest subway system in South America). Most stations have small shops, bars and kiosks, while main hubs interconnect through underground pedestrian walkways with railroad stations, governmental buildings or shopping centres. Some have additional mall-like mezzanine levels, with the Centro Obelisk of Buenos Aires area (3 lines, 4 underground levels), Estación Retiro, Estación Constitución, Estación Once and Federico Lacroze railway station being the most important ones.

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