Twin cities are a special case of two neighboring cities or urban centres that grow into a single conurbation – or narrowly separated urban areas – over time. There are no formal criteria, but twin cities are generally comparable in status and size, though not necessarily equal; a city and a substantially smaller suburb would not typically qualify, even if they were once separate. Tri-cities and quad cities are similar phenomena involving three or four municipalities.
A common – but not universal – scenario is two cities that developed concurrently on opposite sides of a river. For example, Minneapolis and Saint Paul in Minnesota – one of the most widely known pairs of "Twin Cities" – were founded several miles apart on opposite sides of the Mississippi River, and competed for prominence as they grew.
In some cases, twin cities are separated by a state border, such as Albury (New South Wales) and Wodonga (Victoria) in Australia, on opposite sides of the Murray River. In Pakistan, Islamabad and Rawalpindi are twin cities located in northwestern Punjab region with Islamabad, administratively being part of the Islamabad Capital Territory, and Rawalpindi, part of the province of Punjab. Cities on opposite sides of international borders sometimes share enough cultural and historical identity to be seen as twins, such as Haparanda (Sweden) and Tornio (Finland), Leticia (Colombia) and Tabatinga (Brazil), or Valga (Estonia) and Valka (Latvia).
In some cases twin cities eventually merge into a single legal municipality, such as Buda and Pest merging in 1873 into Budapest, Hungary; Brooklyn being annexed by New York City in 1898; or the three ancient cities of Hankou, Hanyang, and Wuchang joining in 1927 into Wuhan.
As a single urban area, twin cities may share an airport whose airport codes include both cities' initials, e.g., DFW (Dallas–Fort Worth), LBA (Leeds - Bradford), MSP (Minneapolis–Saint Paul), RDU (Raleigh and Durham), and CAK (Akron–Canton).
See also: Border town.
| Border towns | Countries | |
|---|---|---|
| / | ||
| Victoria Falls and Livingstone |  Zimbabwe /  Zambia |
| Border towns | Countries | |
|---|---|---|
| Astara and Astara |  Azerbaijan / | |
| Dandong and Sinuiju |  China / | |
| Manzhouli and Zabaykalsk | China / | |
| Heihe and Blagoveshchensk | ||
| Dongxing and Mong Cai | China / | |
| Hekou and Lao Cai | ||
| Johor Bahru and Singapore[1] |  Malaysia /  Singapore | |
| Vientiane and Nong Khai |  Thailand / | |
| / | ||
| Al Ain and Al Buraimi |  United Arab Emirates /  Oman | |
| Agartala and Akhaura | / |
| Border towns | Countries | |
|---|---|---|
| Vienna and Bratislava. This is an example of capital cities of neighboring nations being twin cities of one another. |  Austria /  Slovakia | |
Austria /  Slovenia | ||
 France /  Belgium | ||
| Mouscron and Tourcoing | ||
| Wervik and Wervicq-Sud | ||
 Croatia /  Bosnia and Herzegovina | ||
 Czech Republic /  Poland | ||
| Skien and Porsgrunn. Together with Tollnes, Gulset and Åfoss they form the Grenland metropolitan area |  Norway / Norway | |
 Denmark /  Sweden | ||
 Estonia /  Latvia | ||
| Estonia / | ||
 Finland / | ||
| Finland / Sweden | ||
France /  Germany | ||
 Spain / France | ||
| Poland / Germany | ||
| Guben and Gubin | ||
| Heringsdorf and Świnoujście | ||
 Switzerland / Germany | ||
| Laufenburg (Baden) and Laufenburg, Aargau separated by the Rhine River (used to be one city until 1801/1802). | ||
 Hungary / Slovakia | ||
| Komárno and Komárom | ||
 Ireland /  United Kingdom | ||
 Italy / Slovenia | ||
| Rome and Vatican City. Vatican City is the only sovereign state surrounded entirely by a single city, Rome. The Vatican is an area in Rome. It was part of Italy until 1929, when Pope Pius XI and Benito Mussolini signed the Lateran Treaty. | Italy / | |
 Netherlands / Germany | ||
| Spain / United Kingdom | ||
| Switzerland / Germany / France |
| Twin towns | Country | |
|---|---|---|
| Cairo and Giza.[2] Triple cities if counting Shubra El Kheima. |  Egypt | |
| Port Said and Port Fuad | ||
| Sekondi-Takoradi |  Ghana | |
| Johannesburg and Pretoria, Gauteng Province |  South Africa |
| Twin towns | Country | |
|---|---|---|
| Victoria and Kowloon, colonial Hong Kongalthough, in both colonial Hong Kong and the Hong Kong Special Administrative Region, Victoria is the only city recognised by law; they were widely considered to be separate cities until at least the mid-1970s.[7] | ||
| Wuhan (merger of Wuchang, Hankou, Hanyang) | China | |
| Chirala-Perala |  India | |
| Bangalore Cantonment and Bengaluru Pete along with their suburbs merged to form modern Bangalore | ||
| Fukuoka (merger of east side of Naka river, Hakata, and the west side, Fukuoka) |  Japan | |
| Ise (merger of Uji, Yamada) | ||
| Joetsu (merger of Takada, Naoetsu) | ||
| Naha and Shuri, Okinawa, once separate cities. Shuri became integrated as a district of Naha. | ||
| Saigon and Cholon, merged into Saigon-Cholon, now Ho Chi Minh City. |
| Twin towns | Country | |
|---|---|---|
| Knokke and Heist-aan-Zee. United into Knokke-Heist | Belgium | |
| Gradec and Kaptol. United into Zagreb | Croatia | |
| Frýdek and Místek. United into Frýdek-Místek | Czech Republic | |
| Barmen and Elberfeld. United into Wuppertal. | Germany | |
| Kouvola and Kuusankoski. United into Kouvola. | Finland | |
| West Berlin, West Germany and East Berlin. United into Berlin. | ||
| Buda and Pest. United into Budapest, | Hungary | |
| Bielsko and Biała. United into Bielsko-Biała. | Poland | |
| City of London and City of Westminster. Absorbed into London. | United Kingdom | |
| Berwick-upon-Tweed and Tweedmouth, until the former was taken by England from Scotland. | ||
| Äänekoski and Suolahti. United into Äänekoski. | Finland |
| Twin city | Country | |
|---|---|---|
| Lloydminster, Alberta/Saskatchewan |  Canada | |
| Thunder Bay, Ontario | ||
| Saginaw and East Saginaw, Michigan |  United States | |
| Stanwood and East Stanwood, Washington | United States | |
| Brooklyn and New York City, New York | United States |
| Twin cities | Country |
|---|---|
| Carmen de Patagones and Viedma |  Argentina |
| Paraná, Entre Ríos and Santa Fe | |
| Americana, São Paulo and Santa Bárbara d'Oeste |  Brazil |
| Juazeiro and Petrolina | |
| Olinda and Recife | |
| Vila Velha and Vitória | |
| Concepción and Talcahuano |  Chile |
| Coquimbo and La Serena | |
| Valparaiso and Viña del Mar | |
| Pedro Juan Caballero and Amambay |  Paraguay |
| Callao and Lima |  Peru |
| Acarigua and Araure | |
| Guarenas and Guatire |
| Twin city | Country | |
|---|---|---|
 Australia | ||
| Kalgoorlie and Boulder | ||
| Perth and Fremantle | ||
| Townsville and Thuringowa | ||
| Napier and Hastings |  New Zealand |
See main article: Tri-Cities (disambiguation).
| Border towns | Bordering countries |
|---|---|
| Xinhui, Taishan, Kaiping, and Enping together formed Siyi area in Jiangmen, Guangdong | China |
| Helsinki, Espoo, Kauniainen and Vantaa in Uusimaa; together form the largest metropolis in the country and its actual capital area. | Finland |
| Pattaya-Chonburi Metropolitan Area consists of the City of Pattaya, Town of Chonburi, Portal town of Laem Chabang and Town of Sattahip on the west coast of Chonburi Province, Thailand | Thailand |
| The West Yorkshire Built-up Area consists of the cities of Leeds, Bradford and Wakefield, and the large town of Huddersfield, United Kingdom. | United Kingdom |
| The Florence-Muscle Shoals Metropolitan Area in Alabama, is locally referred to as "the Quad Cities", with Florence, Muscle Shoals, Sheffield, and Tuscumbia, Alabama. Formerly, when Muscle Shoals was a mere village, this region was known as "Tri-Cities", Alabama. In fact, all except Florence are incorporated as towns. | United States |
| Quad Cities of Davenport and Bettendorf, Iowa, and Rock Island and Moline, Illinois. It also includes a fifth member, East Moline, Illinois. | |
| Allentown/Bethlehem, Pennsylvania and Easton, Pennsylvania/Phillipsburg, New Jersey; the collective area is often called the Lehigh Valley | |
| The Quad Cities of Minnesota, consist of Virginia, Eveleth, Gilbert, and Mountain Iron. | |
| The cities of Pullman, Washington, Moscow, Idaho, Lewiston, Idaho and Clarkston, Washington, have marketed themselves as "Quad Cities."[10] |
| Border towns | Country |
|---|---|
| The Triangle Region, consisting of Billund, Fredericia, Haderslev, Kolding, Middelfart, Vejen and Vejle. | Denmark |
| The Ruhr district consisting of Dortmund, Essen, Duisburg, Bochum, Oberhausen, Mülheim, Bottrop, Gelsenkirchen and Herne in its core. | Germany |
| The cities of New Delhi, Noida, Greater Noida, Ghaziabad, Gurgaon and Faridabad have formed a huge metropolitan area known as National Capital Region (India). | India |
| The cities of Mumbai, Thane, Navi Mumbai, Kalyan-Dombivli, Mira-Bhayandar, Vasai-Virar, Panvel, Bhiwandi, Ulhasnagar, Ambarnath and Badlapur have formed a huge Mumbai Metropolitan Region. | |
| The cities of Kuala Lumpur, Petaling Jaya, Subang Jaya, Puchong, Shah Alam, Klang, Port Klang, Putrajaya, Cyberjaya and Kajang have formed a huge metropolitan area (around the size of Singapore) known as Greater Kuala Lumpur. | Malaysia |
| The cities of Karaganda, Temirtau, Shakhtinsk, Abai, Saran, Topar, Dolinka, Shahan, Kokpekti, and Novodolinsky form an industrial-mining area known since Soviet times as Karbass (Karaganda coal basin). |  Kazakhstan |
| Illinois and Iowa: The cities of Davenport and Bettendorf in Iowa; Rock Island, Moline and East Moline in Illinois form a metropolitan area known as the Quad Cities. | United States |
| Michigan and Wisconsin include the 6 cities of Iron Mountain, Kingsford, Quinnesec (in Michigan), Aurora, and Niagara (in Wisconsin). The area is collectively known as the Iron Mountain Area. | |
| Virginia Norfolk, Chesapeake, Hampton, Newport News, Portsmouth, Suffolk, and Virginia Beach; the cities' collective metropolitan area is often called Hampton Roads |
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