Ever since the dawn of agriculture humankind has banded together in cities. Increased cooperation and opportunity made the city appealing when growing your own food was no longer necessary. As more people moved to cities, they grew throughout the centuries to some of the megacities we know today.

Having the title of the world’s largest city has historically been very prestigious; look at Constantinople (Istanbul), London, Rome, New York or Beijing, all whom have held this title previously. While in the past it may have been blindingly clear which city was the largest, in the 21st century the lines are somewhat blurry. To establish which city truly is the largest today we first must decide what we mean by the word ‘city’.

What is a City?

Several definitions are applicable and you will get a different answer depending on where you are in the world and to whom you speak. First is the city proper, a clearly defined administrative area, usually not representative of the true size of a city. There is also the metropolitan area, defined roughly by the habits and movements of the population and labour market around a main centre. This can include numerous surrounding towns around a main hub, or even a number of equally important hubs. Yet another definition is an urban area, an attempt to ignore territorial boundaries of any kind and focus on a more-or-less contiguous area of dense population.

But wait, there’s more. Beyond this we start considering the term conurbation, which is essentially a number of cities that have grown together to form a single continuous urban agglomeration where transport and labour markets merge. This is becoming quite common in the 21st century. Beyond even this is a megalopolis, a chain or culmination of metropolitan areas that, like a conurbation, have labour markets and transportation links that blend into one another but on a far larger scale. We’ll look at these definitions to help decide which city truly is the largest.

Times Square, New York City
Credit: Terabass

Times Square, New York City

The City Proper Problem

Given that the city proper is clearly defined by a political boundary, this type of city is the easiest to understand effectively. As of 2014, it is generally accepted that the administrative city of Shanghai, China is the largest with roughly 24,150,000 people. This figure is changing rapidly due to Shanghai’s amazing growth, much like other Chinese cities. Using this metric, Karachi and Beijing make up the next two, though in which order they rank is open for some debate.

The main problem with using city proper as a ranking metric is that it very rarely represents the true nature of an area. Perth, Australia for example has a city proper population of only around 17,000 due to its tiny administrative border, whereas the generally accepted population of Perth is around 1,700,000 - one hundred times larger. This same problem is evident worldwide in Paris, New York and Tokyo for example, where the city proper is often three, four or even five times smaller than what most would consider the actual population.

Shanghai, China
Credit: Nicholas Poon

Shanghai, China

Metropolitan Areas and Urban Areas

These two metrics are being evaluated together because they are often exactly the same thing. Depending on a huge variety of factors, a city’s population using both of these definitions could be larger or smaller than the other. Factors that determine how a city grows such as zoning restrictions, natural landscapes, borders or cultural differences will alter what is counted or calculated by different organisations.

In both the metropolitan area and urban area definitions, the largest city in the world is without any doubt Tokyo, Japan – called the Greater Tokyo Area. Varying statistics put its total population somewhere between 32,000,000 and 37,000,000, depending on which outer-lying cities are included. To put this in perspective, the upper margin of these estimates is equivalent to the entire populations of Canada, Poland or Algeria, or about the same as California. Greater Tokyo stretches across a vast area of about 13,500 square km (5,000 square miles) – larger than the state of Maryland.

Behind Tokyo in these definitions are Seoul, South Korea (the Seoul Capital Area), Jakarta, Indonesia, Greater Mexico City, Mexico and Delhi, India (the National Capital Territory of India). All of these areas have at least 20,000,000 inhabitants by either method but are a long way from equalling Tokyo in any way. The domination of Greater Tokyo here has generally meant that many, or even most consider it to be the largest city in the world today as it has been ever since it grew larger than New York during the 1960s.

Tokyo Megacity
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Ginza, Tokyo, Japan
Credit: Francisco Diez

Ginza, Tokyo, Japan

The New Conurbations

What many don’t realise, however, is that we as a species are moving into a new era of city inhabitancy. As of 2010 over 50% of the human population lives in cites– the first time in history this has happened. This is expected to rise to over 70% by 2050, which will equate to 6.5 billion people living in cities alone, the same population as the entire world as recently as 2004. Many of these new residents will live in what are becoming known as conurbations – large swathes of urban mass comprised of multiple cities and towns that have grown into one another but are not necessarily continuously urban throughout. Until recently, these phenomena didn’t really occur, but now are quite common and have every right to be considered cities by way of labour market and transportation patterns.

Conurbations are typically anchored by a major metropolitan area and include nearby cities that are generally smaller. These types of cities are harder to define than those above, and as such it’s difficult to say which is the largest. An even bigger consideration of Tokyo, sometimes called Kanto is likely the largest, with upper estimates of around 43,000,000 people – almost equivalent to the population of Spain. The only serious competitors would be the regions around Beijing/Tianjin, Shanghai, and Guangzhou/Shenzhen/Hong Kong – all in China. Whether these would be considered conurbations or Megalopolises is often debated.

Guangzhou, China
Credit: Azwari Nugraha

Guangzhou, China

The Question of the Megalopolis

The Megalopolis had been theorised as far back as 1918 in a book, perhaps appropriately, about the over-development of urban areas. It was first used to describe the chain of cities (which back then were not even remotely close to merging) between Boston and Washington, D.C., including New York, Baltimore and Philadelphia. Today, this chain has been realised and is called the Northeast Megalopolis, which in many places is blending into a continuous form. Currently around 50,000,000 people live here – 17% of the population of the United States.

For a long time the Northeast Megalopolis was the only true example of this extreme urbanisation over hundreds of miles. In the 21st century however there are other, larger examples that arguably could be considered cities depending on integration within them.

The three contenders in China are the Pearl River Delta centred on Guangzhou, Shenzhen and Hong Kong (perhaps 80,000,000 people, though upper estimates have been as high as 120,000,000), the Yangtze River Delta centred on Shanghai (upwards of 88,000,000 people) and the Bohai Economic Rim around Beijing and Tianjin (upwards of 67,000,000 people). Japan has what they call the Taiheiyo Belt, stretching from Tokyo in the north 1200km south to Fukuoka including Osaka, Nagoya and Kyoto, and is home to around 80,000,000 people. The western half of the island of Java, Indonesia centred on Jakarta houses up to 52,000,000 people and is growing rapidly, with the Northeast in the United States not far behind.

The only other area to consider is the Blue Banana, a massive curved region of Europe stretching between Manchester and Liverpool in the north, through London, The Netherlands and Belgium, the Rhine-Ruhr in Germany, through Switzerland and including the entirety of Northern Italy. Estimates suggest a total population of somewhere between 110 and 120 million people. While unlikely to ever be considered a ‘city’ by anyone, its dense corridor of industry and urban areas are undeniably connected and commuting between many of the areas is commonplace.

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Credit: NASA

So Which City Is It?

Opinion is greatly divided on this question and this topic as a whole. In such a dynamic world where countries and cities are changing constantly, keeping track of statistics of this magnitude is difficult and time consuming, not to mention the very human nature of competition. By most sensible evaluations, Tokyo, Japan remains the world’s largest city, but over the coming decades we may see this change in the minds of many. Whether or not any of these places are actually nice places to live is an entirely different question. I’ll leave you with a summation of the largest from each category so you can decide for yourself.

 Largest City Proper:

  • Shanghai, China - 24,150,000
  • Beijing, China - 21,150,000
  • Karachi, Pakistan - 21,150,000

Largest Metropolitan Area:

  • Greater Tokyo Area, Japan - ~37,000,000
  • Seoul Capital Area, South Korea – 25,900,000
  • New York City Metropolitan Area, U.S.A - ~23,600,000

Largest Conurbation:

  • Kanto Region (Tokyo), Japan - ~43,000,000
  • Greater Shanghai, China – 29,400,000
  • Jabodetabek (Jakarta), Indonesia – 28,500,000

Largest Megalopolis (unclear):

  • Blue Banana (Europe) - ~110,000,000
  • Pearl River Delta (China) - 80,000,000 – 120,000,000         
  • Yangtze River Delta (China) - ~88,000,000
  • Taiheiyo Belt (Japan) - 83,000,000