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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, 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 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:
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.
Sydney has a series of underground shopping malls around the underground station Town Hall. The tunnels run south to the George Street cinema district, west under the town hall, and north to Pitt Street Mall through the Queen Victoria Building. The northern branch links Queen Victoria Building with Galleries Victoria, Sydney Central Plaza (which in turn links internally above ground to Westfield Centrepoint, Imperial Arcade, Skygarden, Glasshouse, and the MLC Centre). The linked centres run for over 3 km (2 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.
The cold climate makes underground pedestrian malls quite useful.
- Calgary has an elevated series of walkways instead of underground in its +15 system. The system links many of the buildings in downtown and connects to many accomodations including access to one of Calgary's busiest malls, The Core Shopping Centre.
- The +15 is the second most extensive skyway system in the world with 59 bridges totalling to an estimated length of 16 kilometres.
- Edmonton has a small system of tunnels and above-ground skyways called the Pedway connecting buildings and LRT stations of the downtown core.
- Halifax (Downtown Halifax Link) where no point is more than 10 minutes casual walking distance from any other one.
- Montreal Underground city, or la ville souterraine in French, is the largest 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, the Bell Centre hockey arena, museums, seven metro stations, two train stations (Lucien-L'Allier and Gare Centrale), a bus 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.
- The network began as a connection between Place Ville Marie, the Queen Elizabeth Hotel and the Gare Centrale.
- 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.
- Eight metro stations link to smaller networks that are not yet part of the central network, such as Berri UQAM in the eastern part of downtown and Pie-IX which links venues from the 1976 Summer Olympics. Additionally, other underground networks are now part of the metro system, such as the La Cité housing and retail complex.
- Ottawa's Carleton University has a five kilometer underground tunnel complex which connects ten residence buildings with other buildings on its main campus. The city also has an underground concourse at Place de Ville office complex in the downtown, connecting 4 office buildings and 2 hotels stretching 2 city blocks. There are plans to expand the underground connections after the planned LRT metro (3 downtown subway stations) is built.
- Saskatoon - On the campus of the University of Saskatchewan a tunnel system connects several of the building on campus, this us augmented with overhead walkways that further extend the network.
- St. John's, Newfoundland and Labrador - At the main campus of Memorial University of Newfoundland are the MUNnels, a tunnel system, in which all the main buildings are connected, though there are also some elevated walkways.
- Toronto (PATH), comprises 27 km of walkways and 1,200 shops. It links many important buildings and attractions downtown to six TTC 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 on Bloor Street.
- Vancouver has two shopping malls, Pacific Centre and Vancouver Centre, that are interconnected and extend over three city blocks, containing more than 200 stores that weaves above and below ground level. These malls are also connected to Granville SkyTrain Station on the Expo Line and Millennium Line and Vancouver City Centre Skytrain Station on the Canada Line. Other connections exist between Skytrain stations and surrounding buildings such is the case with the Burrard Station connections to the Bentall Centre and the Royal Centre and Waterfront Station's links with Canada Place and the Sinclair Centre.
- Winnipeg has a smaller (mainly commercial office) area located underground in the downtown core below Portage 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 the skyway system known as the Winnipeg Walkway. Also the University of Manitoba has underground tunnels for the students to travel building to building.
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.
- Beijing built an extensive tunnel network called the Underground City (Chinese: 地下城; pinyin: Dìxià Chéng) during the Sino-Soviet conflict, supposedly covering 85 km², falling into disuse in the 1970s. It has been recently[when?] opened to the public and tourists. There are rumors it was used by the army during the Tiananmen incident. As of 1 July 2009, all "official" remaining entrances appear to be closed.
- Shanghai has a few underground networks, most notably at the People'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 and Xujiahui stations are directly connected to shopping centers, and the Lujiazui station is connected to the Bank of China tower.
- Qingdao has two small underground shopping areas, one at the head of the Zhanqiao (pier) and one west of the Qingdao guest house.
- Harbin has a number of large, multi-level underground shopping areas, originally built for air defence. 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.
- Hong Kong: Many MTR stations in Hong Kong form extended underground networks connecting to buildings and major shopping malls in the neighbouring areas. The stations themselves house a number of retail shops. Notable examples are the Central–Hong Kong stations and the Tsim Sha Tsui–East Tsim Sha Tsui stations.
- Helsinki underground covers the central railway station area, two subway stations (Rautatientori, Kamppi) and shopping malls. The Kamppi metro station is integrated with the Kamppi Center (55,500 m²) 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. The underground network has connections to the nearby Forum shopping centre and Sokos and Stockmann department stores.
- Three other subway stations in Helsinki have similar, smaller undergrounds: Kaisaniemi, Hakaniemi and Sörnäinen.
Paris: The Forum des Halles is a partially underground multiple story commercial and shopping center, opened in 1979. The building is connected to the underground station Chatelet-Les-Halles, central hub of Paris's express metro system, the RER. There was more than 300 km (186 mi) of a network of catacombs, started as limestone quarries and later for burials, used as safe passageways in times of revolution.
- Frankfurt am Main: Underground shopping malls, called 'B-Ebene' in Frankfurt, of considerable size are found at Hauptbahnhof (central station) and Hauptwache.
- Hamburg: The Jungfernstieg 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.
- Stuttgart: There is a large underground shopping mall (Klettpassage) connecting the Hauptbahnhof (central station) with the main shopping street, the Königstraße.
- 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.
Gibraltar has a longer length of road underground than it does on the surface. The Rock is riddled with tunnels, many built during World War II, including hospitals, etc.; some date to Napoleonic times.
In Thessaloniki, coexist Hellenistic, Roman, Byzantine and Ottoman monuments that bear witness to the city history and its significance. Several of the underground secrets of Thessaloniki have been discovered and emerged, while restoration work is under process. Although the final result is impressive with underground monuments such as the Catacombs of St. John and the underground museum of the Agora, they do not comprise highlights for the city and access is still very limited or not permitted even to the locals by the Archaeological Department of the Thessaloniki underground Metro project.
- Ancient Rome had a network of catacombs, ancient Jewish and Christian underground burial places near the city.
- Naples has many chambers and tunnels beneath the city, including channels and reservoirs for water, and catacombs.
The top five largest underground "cities" (地下街, chikagai) in Japan are all shopping districts:
- Crysta Nagahori in Chūō-ku, Osaka — 81,765 m2 (880,111 sq ft)
- Yaesu Chikagai in Chūō, Tokyo — 73,253 m2 (788,489 sq ft)
- Kawasaki Azalea in Kawasaki-ku, Kawasaki — 56,704 m2 (610,357 sq ft)
- Central Park Chikagai in Naka-ku, Nagoya — 56,370 m2 (606,762 sq ft)
- Diamor Osaka in Kita-ku, Osaka — 42,977 m2 (462,601 sq ft)
- Osaka has enormous underground networks in the Umeda, Namba, and Shinsaibashi districts, in which Umeda alone includes over 1,200 retail stores and restaurants, as well as subway and intercity rail stations.
- See also Alice City.
- Tokyo's subway lines are owned by Tokyo Metro (9 lines) and Toei (4 lines), mostly within the 23 special wards. Near the center of the city, connecting passages between stations that span a few blocks exist for commuters. Stations such as Shinjuku and Shibuya have underground shopping malls. Tokyo's network of tunnels is seen as one of the many megalopolis features of the city.
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 the Amsterdam central station, which connects to the city's metro system.
- Maastricht: Originally a casemate, the kazematten of Maastricht form a 14 km (9 mi) long network of tunnels underneath the western part of the city. This tunnel network has mainly been used for military purposes. The main construction period of these tunnels lasted from 1575 to 1825. The newest sections of the tunnel network was dug as late as the middle 20th century, built in the Cold War as a shelter for citizens in the event of a nuclear strike on the city. Another, far more extensive, system of tunnels with a length over 200 km (124 mi) and 20,000 individual corridors lies just west of Maastricht; this is referred to as the Caves of Maastricht (Dutch: Grotten van Maastricht). These man-made 'caves' were used as Marl quarries from the 13th century onwards. In World War II, these caves were used to hide large quantities of paintings from the Germans, even including the Nachtwacht. 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.
The Metro Rail Transit in Metro Manila is expanding its underground MRT malls and they mainly serve is to escape the heat, advertising area, some boutiques and food stalls, and as street crossings. In the capital city of Manila, Quiapo's underground system serves as street crossings and underground mall. In Makati City, aside for street crossings, during heavy rains, it serves as flood control to avoid flood above the streets.
In downtown Warsaw, a network of underground tunnels filled with shops and bars connects railway stations Warszawa Centralna, Warszawa WKD and Warszawa Śródmieście, as well as nearby bus and tram stops along Aleje Jerozolimskie, underground levels of Złote Tarasy mall and shopping gallery under Centrum LIM skyscraper. There's a nearby separate underground commercial passage under Aleje Jerozolimskie/Marszałkowska crossroads.
- Moscow: "Okhotnyi Ryad" (Охотный Ряд) four-level underground shopping mall (29,000 m2 (312,153 sq ft)) linked to Metro station of same name.
- Moscow Metro 2 is a purported secret underground metro system in Moscow built supposedly during (or from) the time of Joseph Stalin.
- Extensive underground networks exist around most major stations of the Mass Rapid Transit, such as the one at the Raffles Place MRT Station with direct underground connections to 19 buildings in the busy Raffles Place area. Expanding the network is the first phase of a new subterranean network linking the station to the up-coming One Raffles Quay development and with provisions to extend it into the Marina Bay new downtown extension for a complex underground pedestrian network across the entire downtown area.
- The CityLink Mall offers over 60,000 square feet (5,600 m2) of underground retail space and connects the City Hall MRT Station with Suntec City, the Esplanade - Theatres on the Bay, and other developments in the Marina Centre area. It is also linked to the Esplanade MRT Station on the Circle MRT Line.
- The Orchard Road shopping belt is connected by underground linkways often with commercial space, particularly around the three MRT stations serving the district, namely Orchard , Somerset , and Dhoby Ghaut . Plans are in place to link all buildings along the road into a continuous underground network on both sides of the over four kilometre long road.
South Korea 
- Seoul has a well-developed underground network. Myeongdong and Hoehyeon underground streets are the most famous; they are connected to Hoehyeon Station and Myeongdong Station
- It is planned to build a larger underground city in Gangnamdaero, the border between Gangnam District and Seocho District.
- In Barcelona, there's an abandoned underground mall near Plaça de Catalunya called Avinguda 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, some Metro 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 under the old part of Toledo were connected and were used by occultists.
- Geneva contains a large underground shopping centre which also acts to connect separate sections of surface shops.
- St. Gallen's main hospital uses several underground tunnels to connect its buildings, helicopter pad, pharmacies and storage facilities.
- Zürich Hauptbahnhof in Zürich has an underground RailCity shopping mall with full access to the station platforms.
Taipei has underground streets connecting two or more metro stations. In addition, there is a large underground shopping mall near the main train station.
The Bangkok Metro in Thailand is steadily expanding its network of underground MRT malls between far flung exits. Unlike most cities, they mainly serve to escape the heat and as street crossings.
- 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 the Hittites, then later by early Christians as hiding places (see ). They are now archeological and tourist sites but are not generally occupied (see Kaymaklı Underground City and Derinkuyu). 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.
- Istanbul boasts the Roman cisterns, built 2000 years ago for water storage but now a tourist attraction.
Kiev: An underground concourse extends underneath Khreschatyk Street from Maidan Nezalezhnosti to Ploscha L'va Tolstoho. The concourse connects to the Kiev Metro and to the Globe shopping mall beneath Maidan Nezalezhnosti.
United Kingdom 
- Corsham, Wiltshire is the location of the Central Government War Headquarters, code name 'Burlington'. Built in the late 1950s in response to the increasing threat of nuclear warfare during the Cold War, the 35 acres (1,524,600 sq ft) subterranean site was designed to be the main emergency government war headquarters of the UK outside of London and safely house up to 4,000 central government personnel in the event of a nuclear strike.
- In London's redeveloped docklands Canary Wharf tube station, adjacent office towers and shopping malls are connected underground. It is also possible to access two stations of the Docklands Light Railway without going outside;
- 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 at Dover Castle through to Napoleonic, Second and Cold War installations. The Dover Castle complex is the larger, going at least six levels deep and includes a hospital, troops quarters, offices and storage and channel view points. The southern tunnels are mixed between Napoleonic War-era defences (see Dover Western Heights) and Second World War-era defences, with some seafront air raid shelters still used for shop storage today. Many have fallen into disrepair and are now closed to the public, but many are still open.
- London: There are extensive rooms, tunnels and chambers known as Churchill War Rooms or Admiralty Citadel beneath Whitehall, created during World War II, and used by Winston Churchill.
- There are extensive underground constructions across Britain, built as air-raid shelters during World War II.
- Edinburgh's old town has extensive rooms, tunnels and chambers beneath some areas; of particular note are the Edinburgh Vaults, where overcrowding led people to construct elaborately interconnected buildings in the vaults of the city's South Bridge.
- In Southport, Merseyside, 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. ;
- in Liverpool, Merseyside, the Williamson's 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'.
- Nottingham has an extensive network of man-made caves, dating back to the Dark Ages.
United States 
- Albany, New York's Empire State Plaza features an underground city which contains banks, a YMCA, restaurants, several food courts, retailers, a police station, a bus station, and a Visitor's Center. The Plaza connects several government buildings to the Egg (a state-owned theater), the New York State Museum, the New York State Library, the Corning Tower (the tallest building between New York City and Toronto), legislative offices, judicial offices, and the Times Union Center. The Empire State Plaza Art Collection consists of 92 large-scale paintings, sculptures, and tapestries at various locations along the main corridor, and features works from the New York School of abstract modern art from the 1960s and 1970s.
- Atlanta, Georgia's “Underground” represents the original surface level of downtown Atlanta; the present streets are raised roadways (viaducts) built in the 1920s. The shopping center Underground 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.
- Boise, Idaho's Capital Mall Complex in downtown Boise 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 Capital 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 Capital 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. Local folklore circulates stories that the Capital Mall Complex may be connected to the original Chinese underground tunnels that were used so Chinese immigrants could move goods to buildings, smuggle opium, and travel after curfew. However, there is little evidence these rumors are true.
- Chicago, Illinois' Chicago Pedway consists of approximately 4 disjointed tunnel systems, the largest covering about 10 blocks, connecting such buildings and transit stations as Metra's Randolph Street Station, the Chicago Cultural Center, the Macy's (former Marshall Field's) store at State and Randolph, Chicago Transit Authority's State Street and Dearborn Street subway stations, City Hall, and the James R. Thompson Center. Pedway Map
- Cleveland, Ohio: The Tower City Center, on the public square at the center of downtown Cleveland, houses a shopping mall with a food court, two hotels, and the Tower City Rapid Transit Station, the central station on RTA's Red, Green, and Blue Lines. The building connects to several office buildings, and also has an enclosed skyway to the Gateway Sports and Entertainment Complex.
- Crystal City, Virginia: A residential and commercial area of Arlington County, Virginia next to Ronald Reagan Washington National Airport, Crystal City features an extensive underground city connecting its hotels, office buildings, and apartment towers and is lined with 173 shops, restaurants, banks, medical, and other services.
- Dallas, Texas' Dallas Pedestrian Network has a network of tunnels connecting buildings in the downtown area.
- Duluth, Minnesota has a small network of skyways and tunnels connecting some buildings, including the Federal Courthouse and Convention Center (DECC).
- Havre, Montana
- Houston, Texas: The seven-mile (11 km (7 mi)) 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 the Houston Theater District. Only one building, Wells Fargo Plaza, offers direct access from the street to the Tunnel; otherwise, you must enter the Tunnel from street-level stairs, escalators, or elevators inside a building connected to it.
- Irvine, California: A network of large tunnels running beneath the University of California, Irvine connects many of the campus' major buildings to a central utility plant.
- Minneapolis and Saint Paul, Minnesota: There are three major systems consisting mostly of above-ground skyways in the Twin Cities. Minneapolis's skyway system covers approximately five miles with 62 skyways. St. Paul's skyway system connects buildings in a 30-block radius in the downtown core.  On the University of Minnesota Minneapolis and St Paul campuses, the Gopher Way connects most buildings and parking structures together using a number of skyway links and underground tunnels. A system of tunnels connects state office buildings around the Minnesota State Capitol.
- New York, New York: Several subway stations have direct access to one or more buildings. Additionally, most of the lower floor of Rockefeller 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 around Times Square and the Port Authority Bus Terminal forms an underground network several blocks in size; much of it is within New York City Subway fare limits.
- Oklahoma City, Oklahoma: The Oklahoma City Underground, formerly the Oklahoma City Conncourse, named after its founder, Jack Conn, is an underground tunnel system connecting nearly all the downtown buildings in a 20-square-block area. The OKC Underground 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 by tunnel or skyway. The original tunnel link was built in 1931 and the system was extended in the 1970s. Offices, shops, and restaurants line the OKC Underground system. It underwent a $2 million renovation in 2006-2007. Upon completion of the renovation, the Conncourse was renamed the Underground.
- Philadelphia, Pennsylvania: There are several underground concourses in Center City built around the Center City Commuter Connection including parts of Suburban Station, Market East Station, the Market-Frankford Line, and Broad Street Line. It is possible to walk from 8th Street to 18th Street east to west and Arch Street to Spruce Street north to south.
- 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: The Mayo Clinic's buildings in the downtown area are interconnected with tunnels and skyways. Other businesses are along the corridors, including a number of hotels 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 the dormitories to the major buildings on campus. Rochester Institute of Technology has several underground networks connecting dormitories and academic buildings together. University of Rochester has an underground network connecting many of its academic buildings.
- Seattle, Washington: Several modern undergrounds and a historical tour exist. The main shopping district around Westlake has an underground connected with the bus tunnel. Another substantial corridor extends from Two Union Square to Rainier Square with connections to hotels, the 5th Avenue Theatre, and many retail shops along the way. The Seattle Underground Tour in Pioneer Square takes visitors on a humorous guided walk showing the original ground level of many buildings in that area.
- Walt Disney World, Florida (southwest of Orlando, Florida) has a network of utility tunnels used by its employees (cast members) for transportation between venues, rest areas, staff preparation, and first aid. The main system is under the Magic Kingdom theme park. Other tunnels lie under Future World at Epcot.
- Washington D.C.: All of the buildings in the United States Capitol Complex are connected by tunnels and underground walkways, which provide easy passage between legislative office buildings, the Capitol building, the Capitol Visitor Center, and the Library of Congress in and inclement weather. The tunnels connecting office buildings are open to the public, but those connecting to the Capitol require security clearance to use. Small electric tramways run from the Capitol building to the Russell, Dirksen, and Hart Senate Office Buildings and to the Rayburn House Office Building. The tunnel between the Capitol and the Cannon House Office Building displays winning pieces of artwork from the annual Congressional Art Competition for high school students.
- Wellesley, Massachusetts: At Wellesley College there is an underground network for teachers and staff to go through which connects all the buildings.
See also 
- [dead link]
- Golany, Gideon S.; Ojima, Toshio (1996). Geo-Space Urban Design. New York, NY: John Wiley & Sons, Inc. ISBN 0-471-16252-3.
- "Maastricht Kazematten". maastrichtunderground.nl. Retrieved 2010-08-19.
- "Kazematten en schuilkelder". VVV Maastricht. Retrieved 2010-08-19.
- "Sint Pietersberg". Stichting Natuurmonumenten. Retrieved 2010-08-19.
- "Historie grotten". maastrichtunderground.nl. Retrieved 2010-08-19.
- "Nachtwacht onder mergel". Municipalty Maastricht. Retrieved 2010-08-19.
- "Schuilkelder voor half Maastricht". Reformatorisch Dagblad. Retrieved 2010-08-19.
- "Rail City".
- Underground Atlanta homepage
- Map of Minnesota State Capitol complex
- "The Conncourse or The Underground". About.com.
- Chambers, Kelley (2007-01-19). "Downtown OKC's Underground set for completion next month". The Journal Record.