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. These tunnels 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. The latter definition encompasses many modern structures, while the former more generally covers tunnel systems from ancient times to the present day.

Underground cities are especially important in cities with cold or hot climates, as they permit the downtown core 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 is 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, while 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 include: