Editing Megacity (section)

===Growth===
[[File:Détail de la maquette de Rome à lépoque de Constantin (5839479770).jpg|thumb|[[Italo Gismondi|Gismondi]]'s model of Rome in the time of [[Constantine the Great|Constantine]]]]
For almost five hundred years, during the period of the [[Roman Republic|Republic]] and later of the [[Roman Empire|Empire]], [[Rome]] was the [[Historical urban community sizes|largest]], wealthiest, and most politically important city of the ancient world, rulling over Europe, Western Asia and Northern Africa.<ref>{{cite web|url=http://www.unrv.com/empire/roman-population.php |title=Roman Empire Population |publisher=Unrv.com |access-date=2010-09-01}}</ref><ref>{{Cite web |title=Pax Romana: Rome's Golden Age |url=https://www.historyhit.com/pax-romana-romes-golden-age/ |access-date=2024-09-18 |website=History Hit |language=en-GB}}</ref> It is often stated that its population passed one million people by the end of the 1st century BC, however, it is debated about whether the population actually reached such a large size.<ref>{{cite web|url=http://home.vicnet.net.au/~ozideas/poprus.htm |title=Population crises and cycles in history |publisher=Home.vicnet.net.au |access-date=2010-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20110405081151/http://home.vicnet.net.au/~ozideas/poprus.htm |archive-date=April 5, 2011 }}</ref><ref>{{cite journal|last=Storey|first=Glenn R.|year=1997|title=The population of ancient Rome|journal=Antiquity|volume=71|issue=274|pages=966–978|doi=10.1017/S0003598X00085859|url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/BACD7DF32B0B77609CD6713B8AF88882/S0003598X00085859a.pdf/div-class-title-the-population-of-ancient-rome-div.pdf|access-date=30 May 2024|archive-date=23 July 2018|archive-url=https://web.archive.org/web/20180723072210/https://www.cambridge.org/core/services/aop-cambridge-core/content/view/BACD7DF32B0B77609CD6713B8AF88882/S0003598X00085859a.pdf/div-class-title-the-population-of-ancient-rome-div.pdf|url-status=bot: unknown}}</ref> Rome's population started declining in 402 AD when [[Honorius (emperor)|Flavius Honorius]], [[Western Roman Empire|Western Roman Emperor]] from 395 to 423, moved the government to [[Ravenna]] and Rome's population declined to a mere 20,000 during the [[Early Middle Ages]], reducing the sprawling city to groups of inhabited buildings interspersed among large areas of ruins and vegetation.

[[Baghdad]] was likely the largest city in the world from shortly after its foundation in 762 AD until the 930s, with some estimates putting its population at over one million.<ref>{{cite web |url=http://geography.about.com/library/weekly/aa011201a.htm |title=Largest Cities Through History |publisher=Geography.about.com |date=2010-06-16 |access-date=2010-09-01 |archive-date=2005-05-27 |archive-url=https://web.archive.org/web/20050527095609/http://geography.about.com/library/weekly/aa011201a.htm |url-status=dead }}</ref> Chinese capital cities [[Chang'an]] and [[Kaifeng]] also experienced huge population booms during prosperous empires. According to the census in the year 742 recorded in the ''[[New Book of Tang]]'', 362,921 families with 1,960,188 persons were counted in [[Jingzhao Fu]] (京兆府), the [[metropolitan area]] including small cities in the vicinity of Chang'an.<ref>''New Book of Tang'', vol. 41 (Zhi vol. 27) Geography 1.</ref> The medieval settlement surrounding [[Angkor]], the one-time capital of the [[Khmer Empire]] which flourished between the 9th and 15th centuries, could have supported a population of up to one million people.<ref>[https://www.independent.co.uk/news/world/asia/metropolis-angkor-the-worlds-first-megacity-461623.html Metropolis: Angkor, the world's first mega-city], The Independent, August 15, 2007</ref>
[[File:Trafalgar Square by James Pollard.jpg|thumb|During the 19th century, [[London]] was transformed into the world's largest city and capital of the [[British Empire]].]]

From around 1825 to 1918 [[London]] was the largest city in the world, with the population growing rapidly; it was the first city to reach a population of over 5 million in 1900. In 1950, [[New York City]] was the only urban area with a population of over 10 million.<ref>{{cite web|url=http://geography.about.com/library/weekly/aa011201g.htm|title=Top 10 Cities of the Year 1950|work=Four Thousand Years of Urban Growth: An Historical Census|author=Tertius Chandler, 1987, St. David's University Press|access-date=2007-03-24|archive-date=2016-04-15|archive-url=https://web.archive.org/web/20160415044639/http://geography.about.com/library/weekly/aa011201g.htm|url-status=dead}}</ref> Geographers had identified 25 such areas as of October 2005,<ref>{{cite web|url=http://www.citypopulation.de/World.html |title=Population statistics |publisher=Citypopulation.de |access-date=2010-09-01}}</ref> as compared with 19 megacities in 2004 and only nine in 1985. This increase has happened as the world's population moves towards the high (75–85%) urbanization levels of [[North America]] and [[Western Europe]].

Since the 2000s, the largest megacity has been the [[Greater Tokyo Area]]. The population of this [[urban agglomeration]] includes areas such as [[Yokohama]] and [[Kawasaki, Kanagawa|Kawasaki]], and is estimated to be between 37 and 38 million. This variation in estimates can be accounted for by different definitions of what the area encompasses. While the prefectures of [[Tokyo]], [[Chiba Prefecture|Chiba]], [[Kanagawa Prefecture|Kanagawa]], and [[Saitama Prefecture|Saitama]] are commonly included in statistical information, the Japan Statistics Bureau only includes the area within 50 kilometers of the [[Tokyo Metropolitan Government Building|Tokyo Metropolitan Government Offices]] in [[Shinjuku, Tokyo|Shinjuku]], thus arriving at a smaller population estimate.<ref>{{cite web|url=http://www.stat.go.jp/english/data/handbook/c02cont.htm |title=Greater Tokyo population statistics |publisher=Stat.go.jp |date=2008-10-01 |access-date=2010-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20080411094023/http://www.stat.go.jp/English/data/handbook/c02cont.htm |archive-date=April 11, 2008 }}</ref><ref>{{cite web|url=http://www.citypopulation.de/World.html |title=Tokyo metropolitan area population statistics |publisher=Citypopulation.de |access-date=2010-09-01}}</ref> A characteristic issue of megacities is the difficulty in defining their outer limits and accurately estimating the populations.

Another list defines megacities as [[urban agglomeration]]s instead of metropolitan areas.<ref>{{Cite web |title=World Megacities - Urban Areas with More than 10,000,000 Population (2015) |url=http://www.demographia.com/db-megacity.pdf |website=Demographia}}</ref> As of 2021, there are 28 megacities by this definition, like Tokyo.<ref>{{Cite web |last=Society |first=National Geographic |date=2018-08-28 |title=The Age of Megacities |url=http://www.nationalgeographic.org/interactive/age-megacities/ |access-date=2022-04-19 |website=National Geographic Society |language=en}}</ref> Other sources list [[Nagoya]]<ref name="citypopulation"/> and the [[Rhein-Ruhr]]<ref>{{cite web |url=http://www.espon.eu/export/sites/default/Documents/Projects/ESPON2006Projects/StudiesScientificSupportProjects/UrbanFunctions/fr-1.4.3_April2007-final.pdf |title=ESPON project 1.4.3 Study on Urban Functions Final Report |access-date=2013-08-07 |url-status=dead |archive-url=https://web.archive.org/web/20150924002318/http://www.espon.eu/export/sites/default/Documents/Projects/ESPON2006Projects/StudiesScientificSupportProjects/UrbanFunctions/fr-1.4.3_April2007-final.pdf |archive-date=2015-09-24 }}</ref> as megacities.