Anunderground city is a series of linkedsubterranean 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 oftunnels 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 toskyway 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.[1][2][3]
Beijing built an extensive tunnel network called theUnderground City (Chinese:地下城;pinyin:Dìxià Chéng) during theSino-Soviet conflict, supposedly covering 85 km2, falling into disuse in the 1970s. It was opened in 2000 to the public and tourists, but closed in 2008 for renovations.[4] As of 1 July 2009[update], all "official" remaining entrances appear to be closed.
Guangzhou has at least 16 different underground networks.[5]
The largest underground network is inZhujiang New Town. It connects the commercial basements of over 35 office towers and malls surrounding the Zhujiang New Town Central Park, and extends toZhujiang New Town,Guangzhou Women and Children's Medical Center,Huangpu Dadao andHuacheng Dadao metro stations. The mall portion under the Zhujiang New Town Central Park alone totals at least 150,000 square metres (1,610,000 sq ft) of commercial space.[6]
Harbin has a number of large, multi-level underground shopping areas, originally built for air defense. The largest is at the roundabout intersection of Xida Zhi street and Hongjun street where three levels of markets following streets from four directions meet under the giant snowflake atrium.
Qingdao has two small underground shopping areas, one at the head of the Zhanqiao (pier) and one west of the Qingdao guest house.
Shanghai has a few underground networks, most notably atPeople's Square metro station, wherein the line 2 station has a second mezzanine full of shops and Line 1 is connected to a large underground shopping gallery at its south end.Shanghai Science Museum stop on line 2 has a large underground shopping area, known for its imitation goods.Huangpi Road South andXujiahui stations are directly connected to shopping centers, and the Lujiazui station is connected to the Bank of China tower.
Shenzhen has quite a few underground shopping malls:
ManyMTR stations in Hong Kong form extended underground networks connecting to adjacentbuildings and at the basement of some majorshopping 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 theTsim Sha Tsui–East Tsim Sha Tsui stations, government-owned pedestrian underpasses and basements of shopping malls, including theK11 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.[10]
In 2017, TheDevelopment Bureau announced that two underground streets will be constructed inKowloon City District, which would connectKowloon City,San Po Kong,Kai Tak station andSung Wong Toi station.[11] 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 theAIRSIDE mall and the Cullinan Sky Mall, both of which connect to Kai Tak Station.
Historical underground cities of Persia includeSamen,Nushabad, and Kariz.
Kish: an underground city by the name ofHidden Pearl was constructed of roads interlinked 20 meters (66 ft.) under the ground. Shops and restaurants are planned to be built.
Isfahan: with the completion ofImam Hosein Metro Station, andJahan Nama Complex, and their eventual underground connection, there would be an underground complex of a length of 300 m formed in Isfahan downtown area. Also, not underground per se, withImam Ali Square's street network being dug underground and a large open space plaza being constructed on the top, the plaza is connected through a series of covered bazaar pathways of a length exceeding 4 km, connecting it toNaqsh-e Jahan Square.
Nushabad: Nushabad has an underground city that served as a refuge during wars.
Sapporo, with its continental climate resulting in snowy winters, has a fairly large underground network in its central core spanning fromSapporo up toSusukino stations. The network also reachesBus Center-Mae Station just within walking distance ofŌdōri Station.
Osaka has enormous underground networks in theUmeda,Namba, andShinsaibashi districts, in which Umeda alone includes over 1,200 retail stores and restaurants, as well as subway and intercity rail stations.
Tokyo has numerous networks of connecting passages surrounding subway stations that span a few blocks for commuters. Stations such asShinjuku andShibuya have underground shopping malls.Shinjuku in particular has a reputation for being so large and complex that even local Japanese get lost there.[13] The top five largest underground "cities" (地下街,chikagai) in Japan are all shopping districts:
TheOrchard Road shopping belt is connected by underground linkways often with commercial space, particularly around the three MRT stations serving the district, namelyOrchard,Somerset andDhoby Ghaut. However, the underground network around the three stations do not connect.[14] Plans are also in place to link towards Bras Basah Road intoSuntec City,Bugis Junction andChinatown.[citation needed]
Seoul has a well-developed underground network. Myeongdong and Hoehyeon underground streets are the most famous; they are connected toHoehyeon Station andMyeongdong Station
An underground mall in Taipei connecting twoTaipei Metro stations
Taipei has two major underground streets connecting two or more metro stations. In addition, there is a large underground shopping mall near the main train station.
Major underground streets that connects multiple metro stations：
Kaohsiung used to host the first underground mall in Taiwan. Opened in 1978, the Kaohsiung underground mall suffered a fire on 18 December 1989, and the underground mall had been closed to public ever since.[16]
Cappadocia contains several historical underground cities carved out of unusual geological formations formed via the eruptions of ancient volcanoes. The cities were initially inhabited by theHittites, then later by earlyChristians as hiding places. They are now archeological and tourist sites but are not generally occupied (seeKaymakli Underground City,Derinkuyu underground city,Özkonak Underground City,Mazı Underground City). The latest large underground city was discovered in 2007 in Gaziemir, Güzelyurt. It was a stopover on the Silk Road, allowing travelers and their camels to rest in safety underground, in a 'fortress' equivalent to a modern hotel.
A typical view from inside theunderground city inDerinkuyu, one of the largest underground complexes inCappadocia. There are few artifacts left from the original builders, mainly just large rocks that were used to block the passage for intruders. Most of the "cities" are corridors, but some places there are rooms large enough to live in, and some rooms that have the cross-like shape of a church, which is probably exactly what they were.
Istanbul has Roman-era cisterns, built 2,000 years ago for water storage. It is now a tourist attraction.
Sydney has a series of underground shopping malls around theTown Hall underground station. The tunnels run south to theGeorge Street cinema district, west under the town hall, and north toPitt Street Mall through theQueen Victoria Building. The northern branch links Queen Victoria Building with Galleries Victoria, Sydney Central Plaza (which in turn links underground toWestfield Sydney and internally above ground to Centrepoint, Imperial Arcade, Skygarden, Glasshouse and25 Martin Place). The linked centres run for over 3 km (1.9 mi). In 2005,Westfield Corporation submitted a development application to link Sydney Central Plaza underground with 3 other properties on Pitt Street Mall and extend the tunnel network by a further 500 m (1,640 ft) or more.
Perth has a small network of underground shopping malls running from theSt Georges Terrace entrance to Trinity Arcade to Murray Street Mall.
The small town ofCoober Pedy in northernSouth Australia has numerousunderground residences and other facilities. The area was and is extensively mined foropal, and the settlers lived underground to escape the scorching daytime heat, often exceeding 40 °C (104 °F).
Melbourne is said to have the largest underground tunnel system in the world spanning over 1,500 km (930 mi), with the clandestine group known as theCave Clan who meet regularly to explore, vandalise, socialise and map out this network. The vast majority of these tunnels are decommissioned or for stormwater purposes.[17]
Skenderija is a cultural, sports and trade center located inSarajevo,Bosnia and Herzegovina. In the area of 70,000 square meters there are multipurpose halls for various sports, concert and cultural venues, and trade areas above ground including square. Underground is a modern shopping center "Privredni grad" (English:Commercial City) with numerous confectionery shops, restaurants, coffee bars and other spaces.[18][19]
TheSarajevo Tunnel (Serbo-Croatian: Sarajevski tunel / Сарајевски тунел), also known as Tunel spasa (Тунел спаса, English:Tunnel of salvation) and Tunnel of Hope, was a tunnel constructed between March and June 1993 during theSiege of Sarajevo in the midst of theBosnian War.
Cellars of Diocletian's Palace, sometimes referred to as the "basement halls", is a set of substructures, located at the southern end ofDiocletian's Palace[20] (now the southernmost part ofSplit Stari grade), that once held up the private apartments ofEmperorDiocletian[20] and represent one of the best preserved ancient complexes of their kind in the world.[21]
Znojmo has a vast labyrinth of underground passageways and cellars known as theZnojmo Catacombs. They were originally developed for defensive purposes.
InHelsinki centre, underground shopping areas cover thecentral railway station area including the underground shopping centreAsematunneli, and two subway stations,Rautatientori andKamppi. TheKamppi metro station is integrated with theKamppi Center (55,000 m2 (592,015 sq ft)) long-distance bus terminal, freight depot and internal parking area, all underground. It features a six-storey shopping complex and a central bus terminal for local buses. Together with these, theForum shopping centre,Sokos andStockmann department stores are all connected together with underground walkways featuring shops and other services.
Themines of Paris are several disconnected networks of more than 300 km (186 mi) of mining tunnels started in the 13th century and dominated by the "large south network" on theLeft Bank, of which 1.7 km (1 mi) was repurposed from 1786 as theCatacombs of Paris ossuary, the final resting place of 6-7 million Parisians.[24] Other parts of the tunnel network have long been closed off for safety reasons, but the tunnels have served as safe passageways during war and revolution, routes forurban explorers, and venues for unauthorized cultural activities.
La Défense, the major business district northwest of the city center built in the 1960s, has an extensive network of commercial passageways under a vast plaza centered on theGare de La Défense and radiating out to connect with surrounding buildings, notably the largeLes Quatre Temps shopping center andCNIT, but enabling access to many buildings of the district.
TheForum des Halles is a partially underground multilevel commercial and shopping center connected to the massive underground transit hubChatelet-Les-Halles. Opened in 1979, passageways extend west under theJardin Nelson Mandela for several city blocks, and within the fare zone of theParis Metro, stretch half a kilometer south to the banks of theRiver Seine.[25]
Naours: 33 metres (108 ft) below thePicardy village of Naours (between Doullens and Amiens), the 28 galleries (2,000 metres (6,562 ft) long) of an ancient limestone quarry (exploited since the 3rd century c.e.) have long been used as shelter by the population seeking refuge from invaders. Occupied by theTriple Entente forces duringWWI, and then used as headquarters by the German Army during theWWII occupation of France, the galleries are now open to visitors.
Arras: duringWorld War I, the French and British Army built a tunnel system (boves) based upon the already existingadits from a formerly usedquarry. Scots and Englishmen used the quarry below the quarter Saint-Sauveur and called it "Glasgow", "Manchester" and "Liverpool". TheNew Zealand Army (bonded with the British Army) used the quarry for constructing another tunnel system below the quarter Ronville and called it "Wellington", "Auckland" and "Nelson".[26] Soldiers from these armed forces hid in the tunnels for several days. On April 9, 1917, 5:30 am, 24,000 soldiers sortied from there to encounter German troops.[27]
Berlin: several buildings on the east side of Friedrichstraße, from Quartier 205 (Friedrichstraße 70) northwards up to Galerie Lafayette are connected to each other. Businesses are on both sides of the underground street so that it appears to be inside a building all the time, even when it crosses Taubenstraße underground.
Extensive underground bunkers still exist all throughout the city centre, although they are largely sealed off and closed to the public.
All of the buildings at the largeCharité Virchow campus are connected via a system of spacious tunnels. In addition to employee use, particularly during inclement weather, there is also a rudimentary robotic system via which mail and packages are delivered across campus.
Frankfurt am Main: underground shopping malls, called 'B-Ebene' in Frankfurt, of considerable size are found at Hauptbahnhof (central station) and Hauptwache.
Hamburg: theJungfernstieg and Rathaus subway stations and several entrances are connected by pedestrian tunnels, some of them contain shops. There is a direct access to the Europapassage shopping mall.
Munich: underground shopping mall at Karlsplatz/Stachus. This combines the underpass that leads to the pedestrian area and the entry to the subway system.
Stuttgart: there is a large underground shopping mall (Klettpassage) connecting the Hauptbahnhof (central station) with the main shopping street, the Königstraße.
InThessaloniki,Hellenistic,Roman,Byzantine, andOttoman monuments coexist underground and several of these have been discovered and merged together. Monuments such as the Catacombs of St. John and the underground museum of theAgora have limited access and many are not permitted to enter even to the locals by the Archaeological Department of the Thessaloniki undergroundMetro project.[28]
In general, many large railway stations house underground hallways featuring shops, restaurants, banks and money exchange offices. A striking example of such stations would be the main hallway of theAmsterdam central station, which connects to the city'smetro system, although due to renovation and re-building it was temporarily (2012–2015) not possible to walk from the subway to the train station without going outside.
Maastricht: originally acasemate, thekazematten of Maastricht form a 14 km (9 mi) long network of tunnels underneath the western part of the city.[29] This tunnel network has mainly been used for military purposes. The main construction period of these tunnels lasted from 1575 to 1825.[29] The newest sections of the tunnel network were dug as late as the middle 20th century, built in theCold War as a shelter for citizens in the event of a nuclear strike on the city.[30]
Caves of Maastricht are a far more extensive, system of tunnels with a length over 200 km (124 mi) and 20,000 individual corridors lies just west of Maastricht; (Dutch:Grotten van Maastricht).[31] These man-made 'caves' were used asMarl quarries from the 13th century onwards.[32] InWorld War II, these caves were used to hide large quantities of paintings from the Germans, even including theNachtwacht.[33] In 1944, construction started on a large public shelter that could have housed 45,000 persons in these caves. The project never saw its completion due to the liberation of Maastricht in the fall of the same year.[34]
InBarcelona, there is an abandoned underground mall nearPlaça de Catalunya calledAvinguda de la Llum, closed since 1990, which had originally been part of a more ambitious project to build an underground city under the centre of Barcelona. Also, someMetro stations or connecting lines in the same station are connected by underground passages over a block in length.
Legend has that the many caves and tunnels inSubterranean Toledo under the old part ofToledo were connected and were used by occultists.
By walking throughStockholm subway stations and indoor shopping malls it is possible to walk indoor through the central business district, partly underground, from Arsenalsgatan subway entrance (Kungsträdgården station) to Kungsbron (north entrance to Cityterminalen bus terminal), covering a distance of between 1 and 2 kilometres.
Kyiv: an underground concourse extends underneathKhreschatyk Street fromMaidan Nezalezhnosti to Ploshcha Ukrainskykh Heroiv. The concourse connects to theKyiv Metro and to the Globe shopping mall beneath Maidan Nezalezhnosti.
Odesa: a ramified tunnel network made from the former quarries that is famous asOdesa Catacombs covers the historical center of Odesa and some suburban areas.
In the redeveloped docklands area,Canary Wharf tube station is connected underground with adjacent office towers and shopping malls. It is also possible to access two stations of theDocklands Light Railway without going outside.
Edinburgh's old town has extensive rooms, tunnels and chambers beneath some areas; of particular note are theEdinburgh Vaults, where overcrowding led people to construct elaborately interconnected buildings in the vaults of the city's South Bridge. There is also an street namedMary King's Close, which was built over in 1753, and is now preserved and open to visitors.[37]
Corsham is the location of theCentral Government War Headquarters, code name 'Burlington'. Built in the late 1950s in response to the increasing threat of nuclear warfare during theCold War, the 35 acres (14 ha) subterranean site was designed to be the main emergency government war headquarters of the UK outside London and safely house up to 4,000 central government personnel in the event of a nuclear strike.
Dover contains a series of interconnecting tunnels, that honeycomb both sides of the Dover Valley, carved into the chalk cliffs. These date from ancient times atDover Castle through to Napoleonic, Second World War and Cold War installations. The Dover Castle complex is the larger, going at least six levels deep and includes a hospital, troop quarters, offices, storage and channel view points. The southern tunnels are mixed between Napoleonic War-era defences, such as theDover Western Heights, and Second World War-era defences, with some seafront air raid shelters still used for shop storage today. Some have fallen into disrepair and are now closed to the public, but many are still open.
InLiverpool, theWilliamson Tunnels included the site of an 'underground house' complete with windows (concealed by work for public opening), and an extant and partially excavated 'banqueting hall'.
InSouthport, Nevill Street has the remainders of an underground shopping street, which can now only be accessed from the cellars of buildings on the current street, which was raised by one storey from the original level. One end of the underground street ended at the Marine Lake, close to the pier entrance.
There are extensive underground constructions across Britain, such asChislehurst Caves, built or repurposed as air-raid shelters during World War II.
The cold-winter northerncontinental climate of much of Canada makes underground pedestrian malls particularly useful in many cities.
Edmonton, Alberta, has a small system of tunnels and above-groundskyways called thePedway connecting buildings andLRT stations of the downtown core.
University of Calgary inCalgary, Alberta, has a small system of tunnels and at-ground and above ground ways. It connects almost all buildings on Campus.
Halifax, Nova Scotia (Downtown Halifax Link), where no point is more than 10 minutes casual walking distance from any other one.
Montreal, Quebec, RÉSO,Underground City, orla ville souterraine in French, is the largest habitable underground network in the world. Its 32 km (20 mi) of tunnel cover more than 41 city blocks (about 12 km2 (5 sq mi)). Access through the RÉSO can be made to apartment buildings, hotels, offices, banks, and universities, as well as public spaces like retail shops and malls, concert halls, cinemas, theBell Centre hockey arena, museums, eightmetro stations, two train stations (Lucien-L'Allier andGare Centrale), abus terminal (Réseau de transport de Longueuil and other transit authorities), and other areas. It connects 80% of office space and 35% of commercial space in downtown Montreal.
More than 2,000 shops and 40 cinemas line the passageways. Tourists often visit attractions in the underground city, which is used by an average of half a million Montrealers per day.
Eightmetro stations link to smaller networks that are not yet part of the central network, such asBerri-UQAM in the eastern part of downtown andPie-IX which links venues from the1976 Summer Olympics.
Carleton University inOttawa, Ontario, has a 5-kilometre (3.1 mi)tunnel network which connects ten residence buildings with other buildings on its main campus.
The city also has an underground concourse at thePlace de Ville office complex in thedowntown business district, connecting 4 office buildings containing over 1,000,000 square feet (93,000 m2) of leasable space, and 2 hotels with 900 rooms combined. There are plans to expand the underground network after theConfederation Line, a light rail line featuring three downtown subway stations, is completed. It is estimated there will be as many as 20 buildings with direct indoor connections to the downtown subway portion, or 4 million square feet of office space, 1,800,000 square feet (170,000 m2) of retail, 1400 hotel rooms and theOttawa Convention Centre.
Saskatoon, Saskatchewan – On the campus of theUniversity of Saskatchewan a tunnel system connects several of the buildings on campus, this is augmented with overhead walkways that further extend the network.
Toronto, Ontario ("PATH"), comprises 29 kilometres (18 mi) of walkways and 1,200 shops. It links many important buildings and attractions downtown to sixTTC subway stations. PATH accommodates 100,000 pedestrians daily, and PATH businesses host the world's largest underground sidewalk sale once annually.
The PATH network in Toronto is the largest underground shopping complex in the world with 371,600 square metres (4,000,000 sq ft).
Toronto also has a separate, smaller "underground city" connecting several building complexes and two subway stations onBloor Street.
Winnipeg, Manitoba, has a smaller (mainly commercial office) area located underground in the downtown core belowPortage and Main. Several of the downtown office towers have subterranean entrances to the complex allowing employees and visitors to bypass the downtown traffic and avoid the cold winter temperatures Winnipeg regularly experiences. The system links with theskyway system known as theWinnipeg Walkway. Also theUniversity of Manitoba has tunnels for the students to travel from building to building.
Charlottetown, Prince Edward Island, has a tiny system. A pedestrian tunnel connects theConfederation Center of the Arts with the Confederation Court Mall. The mall also connects to The Holman Grand Hotel. The Mall is separated into a main section and a much smaller section connected by an overground walkway. This small section of the mall connects to a 338 spotparking garage, which itself connects to the Homburg Financial Building, and has a separate public entry. Apart from the hotel, two additional office buildings are on top and can be assessed through the mall, a building owned byNational Bank, and a building owned byBDC.
Atlanta,Georgia: the "Underground" represents the original surface level of downtown Atlanta; the present streets are raised roadways (viaducts) built in the 1920s. The shopping centerUnderground Atlanta, taking advantage of the former street-level storefronts, covers six city blocks and includes retail shopping and restaurants. It was begun in 1968 and re-opened in 1989 after a financially forced closure.[39]
Boise,Idaho: the downtown sector's Capitol Mall Complex consists of a large system of networked tunnels that connect all the state buildings. The tunnels have walkways and vehicle passageways. The underground area boasts a geothermal power plant, a banking system, extensive dining areas, parking, a dedicated mail room for the Capitol Mall Complex and a fallout shelter. The main hall is decorated with art from local artists that was collected over a thirty-year time frame. This collection is not often seen by the public as access is limited. Recent remodeling of the Idaho State Capitol Building has added new underground wings that are linked to the Capitol Mall. These new wings have offices, meeting rooms, and records storage areas and were designed to support the Idaho legislature when it is in session.
Dayton, Ohio: the academic section ofWright State University's campus contains nearly two miles (3.18 kilometers) of tunnels[42] that link 20 of the 22 buildings. The tunnels were designed to connect the campus without imprinting the surrounding land.
Duluth,Minnesota: the city's downtown sector has an extensive network of skyways and tunnels connecting its buildings, including the Federal Courthouse and Convention Center (DECC).
Havre,Montana: the city has an underground area, called "Havre Beneath the Streets", that operates as a tourist attraction.[43]
Houston, Texas: the seven-mile (11 km)Houston tunnel system is set about twenty feet below Houston's downtown street system and is composed of underground passageways which, with above-ground skywalks, link office towers to hotels, banks, corporate and government offices, restaurants, retail stores, and theHouston Theater District. Only one building,Wells Fargo Plaza, offers direct access from the street to the Tunnel; otherwise, the Tunnel can only be entered via street-level stairs, escalators, or elevators inside a building connected to it.
Irvine, California: a network of large tunnels running beneath theUniversity of California, Irvine connects many of the campus' major buildings to a central utility plant. These tunnels are only accessible to maintenance staff, although there are also publicly accessible tunnels which intersect the utility tunnels, such as the one that goes between the main Information & Computer Science building and the Engineering Tower.[citation needed]
Kansas City,Missouri: the city'sSubTropolis is a 55,000,000 square foot (5,060,000 m³), 1,100-acre (4.5 km²) underground business complex running along the Missouri River. The space was originally part of the Bethany Falls limestone mine, and was later repurposed for use as a commercial underground storage facility.
New York City, New York: severalNew York City Subway stations have direct access to one or more buildings. Additionally, most of the lower floor of theRockefeller Center qualifies as an underground city, as it features connections to subways, an extensive underground concourse, building connections, and several restaurants, all below ground. The area aroundTimes Square and thePort Authority Bus Terminal forms an underground network several blocks in size; much of it is within theNew York City Subway'sfare control. A series of tunnels connectBrookfield Place (New York City) through the World Trade Center's lower levels, to theFulton Center, forming an underground city with several subway stations and many shops and restaurants.
Oklahoma City,Oklahoma: theOklahoma City Underground (formerly the Oklahoma City Conncourse) is a tunnel system connecting nearly all of the downtown buildings in a 20-square-block area. It is one of the most extensive all-enclosed pedestrian systems in the U.S., extending three-quarters of a mile and connecting over 30 downtown buildings via tunnels or skyways. The original tunnel link was built in 1931 and the system was extended in the 1970s. It underwent a $2 million renovation in 2006–2007, after which the Conncourse was renamed the Underground.[46][47]
Philadelphia,Pennsylvania:Center City has several miles of interconnected underground concourses underMarket,Broad, andLocust Streets, andJFK Boulevard. The system includes ninerapid transit andregional rail stations served by 23SEPTA andPATCO lines, and the lower levels of several shopping centers. It is also connected to the lower levels of many office buildings and several department stores and hotels, as well as the customer service counters of the Municipal Services Building. A branch of theUS Post Office is located in theSuburban Station section of the concourse.
Portland,Oregon: there is a group of connected tunnels from the 19th century known as the Old Portland Underground orShanghai tunnels.
Richmond, Virginia: there are a series of connected tunnels between state government buildings in the city of Richmond. Certain passageways are locked off but a good portion of the tunnels are accessible from buildings. The purpose of the tunnels is not generally known; the two most common explanations are that they were built to allow people to move between buildings in inclement weather or that they were built as part of an emergency evacuation plan.
Rochester, Minnesota: theMayo Clinic's buildings in the downtown area are interconnected with tunnels and skyways. Other businesses are along the corridors, including a number ofhotels that often house clinic patients. It is often called a subway, although there are no underground rails in the city.
Rochester, New York:Nazareth College in the southeast portion of Rochester has an extensive underground network of tunnels leading from thedormitories to the major buildings on campus.Rochester Institute of Technology has two tunnel networks linking its residence halls, and its academic buildings, but the two networks are unconnected. TheUniversity of Rochester has an underground network connecting many of its academic buildings.
Vicksburg, Mississippi: during theSiege of Vicksburg in 1863, Union gunboats lobbed over 22,000 shells into the town, destroying nearly all of the town's housing. As a result, over 500 caves were dug into the clay hills surrounding Vicksburg. The Union soldiers later gave the town the nickname of "Prairie Dog Village" due to these caves.
Guanajuato city was built over old silver mines, some of which are used as roads. TheMexico DF metro system has many underground pedestrian walkways connecting stations.
Buenos Aires, capital ofArgentina, has an extensive number of underground cities in itsSubte. 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 CentroObelisk of Buenos Aires area (three lines, four underground levels),Estación Retiro,Estación Constitución,Estación Once, andFederico Lacroze railway station being the most important ones.
Santiago has some elements of an underground city in its "Metro" subway system. While all stations have a small mezzanine level above the tracks for ticket purchase, some key stations have extensive areas of shops and kiosks in addition. Some stations even have an additional mall-like level between the street and the mezzanine levels.
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