Top 10: The largest cities in the world
Our planet is becoming increasingly crowded, as illustrated by these megacities.
After the global population hit eight billion on 15 November 2022, various predictions have been made about when the number of people on Earth will peak. Studies vary, with some suggesting that world population will peak at 8.8 billion people by the middle of this century, before it starts to decline. Other predictions, such as those made by the United Nations, estimate that the world's population could hit more than 10 billion by the 2080s.
In any case, the substantial increase in population has led to significant congestion in several of the world’s largest cities, giving rise to major concerns regarding pollution and overcrowding.
To put this list into some kind of perspective, the population of Greater London, UK, is about nine billion, and New York, USA, is approximately 8.5 billion.
Here are the ten most-populated cities on Earth, and what it is like to live in them.
10. Osaka, Japan - 19.2 million people
Keihanshin Metropolitan Area, which includes Japan's third-largest city Osaka, is home to some 19.2 million people. Historically important as a centre of commerce and industry, the city is still a financial hub home to many large Japanese companies.
Osaka is famed for its food culture and modern architecture, making this popular with tourists. And thanks to a half-decent public transport system that would be unheard of in the UK, the city's Metro manages to carry over 900 million people a year.
It is not all good news though. As with any modern megacity, traffic is a huge issue thanks to overcrowded roads, and decent housing is hard to find... even if you have tonnes of cash.
9. Beijing, China - 19.4 million people
China's second-largest city is one of the oldest cities in the world, and is also home to most of the country's biggest businesses. This has led to huge population growth in the last 50 years, and increasing wealth amongst many of its residents. In fact, Beijing now has the most number of billionaires in world.
However, it's not all good news. Thanks to a combination of industrial pollution, frequent sandstorms and car emissions, many residents in Beijing are often told to stay indoors to avoid the potential health hazards.
More like this
Car use has increased massively over the last ten years, despite an impressive subway system and various bicycle loan projects.
And with a population density of 4,600 people per km, the residents of Beijing probably find it hard to get a moment to themselves.
8. Mumbai, India - 20.1 million people
Mumbai is built on seven islands, and is an historic city that is full of culture and art. It is also home to the Indian film industry (Bollywood), known around the world for its vibrant movies and musical numbers.
Most importantly, it is the commercial and financial capital of India. Most of the largest companies in India are based in Mumbai, which has led to a huge influx of people from rural areas wanting to live there.
This naturally causes some headaches, with poor sanitation and low-quality housing being the main problems. Mumbai also has some of the world’s busiest roads, mainly due to a lack of high-capacity infrastructure and a public transport system that is unable to cope with demand.
7. Dhaka, Bangladesh - 20.2 million people
The capital city of Bangladesh is growing at a fast rate, which is fuelled in part by a thriving publishing industry. This has led to vast high-rise apartments and offices sprouting up all over this sprawling metropolis.
This historic city is the centre of Bengali culture, hosting countless art festivals and religious events throughout the year. It is also home to the government of Bangladesh, as well as historic buildings such as the Nimtali Palace and the Lalbagh Fort.
However, due to its position on the Ganges Delta, Dhaka is somewhat prone to flooding during the monsoon and cyclone seasons.
6. Cairo, Egypt - 20.4 million people
In addition to its historically significant architecture, Cairo is probably best known as the home of one of the ancient wonders of the world; the ancient Egyptian Giza pyramid complex. It is also home to 11 per cent of the population of Egypt.
There are plans in place to build two monorail systems to serve the city, which will help to ease the significant traffic issues that the city currently experiences.
Frequent dust storms and the desert climate makes might sound like a deterrent, but this doesn’t stop people wanting to visit…
5. Mexico City, Mexico - 21.6 million people
Mexico City sits high on the plateau known as the Valley of Mexico, 2,240m above sea level, and is the oldest capital city in the Americas.
The growth of this metropolis is remarkable. In 1900, its population stood at a mere 500,000 people. But due to large numbers of people from rural areas coming to the city looking for work, this ballooned to nine million by the 1970s. Because of a lack of housing, this influx led to large numbers of people setting up illegal shantytowns around the city.
Mexico City is now a centre of business and also a popular tourist attraction, full of museums and places to eat. Amazingly, if Mexico City were an independent country, it would be the fifth-largest economy in South America.
More images from BBC Science Focus:
- In pictures: The ten biggest snakes in the world
- Top ten: Biggest spiders in the world
- Earth's most extreme towns and harshest environments
- Could farming without soil help solve our food crisis?
- Welcome to the most dangerous waters on the planet
4. São Paulo, Brazil - 21.8 million people
It is a bit of a cliché, but São Paulo is a city of huge contrast. A place where extreme poverty meets great wealth, with the biggest skyscrapers of the financial district towering over the slums of the city, known as the favelas.
Water supply issues are a problem in São Paulo, with few natural sources of drinking water in the city. The haphazard nature of the layout of the city and its buildings doesn't help.
However, crime has been falling and air quality has been steadily improving in recent years, making it a nicer place to live for all of its 22 million residents.
3. Shanghai, China - 26.3 million people
Many many years ago, Shanghai used to be a small fishing village. But thanks to its location by the southern estuary of the Yangtze River, it has since grown to be the biggest city in China, and one of the largest in the world.
It is also home to the Nanjing Road shopping district, a mix of modern malls and traditional Chinese stores and food outlets. Its 5.5km streets rank alongside Oxford Street in London and the Champs-Élysées in Paris as one of the busiest commercial areas in the world, with one million people shopping there every day.
2. Delhi, India - 29.3 million people
The National Capital Territory of Delhi (NCT) encompasses the city of New Delhi (the nation's capital), as well as several other regional states.
The city itself has been in existence for over 2,000 years, which brings its own set of problems. Infrastructure is outdated, although there have been many recent road-building projects that have helped to ease traffic.
Pollution from roads and industry is also a big problem in Delhi, as is the standard of housing. It is estimated that 50 per cent of the population live in sub-standard accommodation.
1. Tokyo, Japan - 37.4 million people
The heaving metropolis of Tokyo covers just 13,452km2, meaning that there are 2,642 people in each km on average in the whole of the Greater Tokyo Area. This high density obviously presents problems for its residents in terms of living space and travel.
As to be expected, housing shortages are widespread. Because of this, tiny apartments that measure only 9m2 are becoming increasingly popular amongst younger residents, as they try to locate themselves near to the centre of the city for work.
Getting around the city is very problematic too. The roads are often completely packed in and around the city. Public transport is also often overcrowded and expensive, although it is almost always on schedule.
James Cutmore is the picture editor of BBC Science Focus Magazine, researching striking images for the magazine and on the website. He is also has a passion for taking his own photographs