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. Underground cities may be currently active modern creations or they may be historic including ancient sites, some of which may be entirely or partially open to the public.
The term may also refer to a network of tunnels that connects buildings beneath street level that may house office blocks, shopping centres, 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.
Some cities also have tunnels that have been abandoned.

Asia

China

Many MTR stations in Hong Kong form extended underground networks connecting to adjacent buildings and at the basement of some major shopping malls in the area above. In addition, the stations themselves often house a number of retail shops.
Among such, the largest underground network consists of numerous out-of-system passageways within the station complex connecting the Tsim Sha Tsui–East Tsim Sha Tsui stations, government-owned pedestrian underpasses and basements of shopping malls, including the K11 Art Mall. In whole, the underground network spans almost the entirety of the retail heart of Tsim Sha Tsui, from Canton Road to the West and Chatham Road South to the East, and from Victoria Harbour to the South and Cameron Road to the North.
Previously, additional underground networks have been proposed for Causeway Bay in 2006 and in Kwun Tong under Hoi Yuen Road in 2010. As of 2014, studies are underway for underground networks in Tsim Sha Tsui, Kowloon Park, Victoria Park, Causeway Bay, Happy Valley, Admiralty, Wan Chai and Hong Kong Park. However, as of 2024, only the network in Tsim Sha Tsui had been built.
In 2017, The Development Bureau announced that two underground streets will be constructed in Kowloon City District, which would connect Kowloon City, San Po Kong, Kai Tak station and Sung Wong Toi station. The system would be known as “Kai Tak Underground Shopping Street.” As of 2025, the only portions constructed and operational are the basement portion of the AIRSIDE mall and the Cullinan Sky Mall, both of which connect to Kai Tak Station.

Iran

Historical underground cities of Persia include Samen, Nushabad, and Kariz.