A look inside the most populated cities in the world

As the number of people in cities around the world continues to increases, so does the risk of issues like overcrowding, waste management and resources.

More than half of the world's population was living in urban settlements in 2016, according to the United Nations' The World's cities data booklet. The booklet defines a city using the term 'urban agglomeration,' which considers the extent of the contiguous urban area, or built-up area, to determine the city's boundaries.

SEE ALSO: East Coast city tops list of most energy efficient US cities

As of 2016, the world had 31 megacities -- cities with 10 million inhabitants or more -- and they are growing, in both size and number.

According to the U.N., the world is expected to add 10 new megacities by 2030. Tokyo is expected to remain the world's largest city in 2030, despite a projected decline of nearly 1 million inhabitants.

Check out the world's 31 megacities:

32 PHOTOS
The most overcrowded cities in the world
See Gallery
The most overcrowded cities in the world

31. Lima, Peru

2016 population: 10,072,000

(Photo credit should read CRIS BOURONCLE/AFP/Getty Images)

30. Madras, India

2016 population: 10,063,000

(Photo credit should read STR/AFP/Getty Images)

29. London, United Kingdom

2016 population: 10,434,000

(Photo credit Graham Mitchell/Barcroft Images / Barcroft Media via Getty Images)

28. Bangalore, India

2016 population: 10,456,000

(Photo credit MANJUNATH KIRAN/AFP/Getty Images)

27. Jakarta, Indonesia

2016 population: 10,483,000

(Photo by Jefri Tarigan /Anadolu Agency/Getty Images)

26. Shenzhen, China

2016 population: 10,828,000

(Photo by Per-Anders Pettersson/Getty Images)

25. Paris, France

2016 population: 10,925,000

(Photo via REUTERS/Gonzalo Fuentes)

24. Tianjin, China

2016 population: 11,558,000

(Photo by Zhang Peng/LightRocket via Getty Images)

23. Kinshasa, Democratic Republic of the Congo

2016 population: 12,071,000

(Photo credit should read EDUARDO SOTERAS/AFP/Getty Images)

22. Moscow, Russian Federation

2016 population: 12,260,000

(Photo by Alexander Shcherbak\TASS via Getty Images)

21. Los Angeles-Long Beach-Santa Ana, USA

2016 population: 12,317,000

(Photo credit RINGO CHIU/AFP/Getty Images)

20. Rio de Janeiro, Brazil

2016 population: 12,981,000

(Photo credit VANDERLEI ALMEIDA/AFP/Getty Images)

19. Guangzhou, Guangdong, China

2016 population: 13,070,000

(Photo by Sun Tao/VCG via Getty Images)

18. Manila, Philippines

(Photo by Veejay Villafranca/Bloomberg via Getty Images)

17. Lagos, Nigeria

2016 population: 13,661,000

(Photo by Frederic Soltan/Getty Images)

16. Chongqing, China

2016 population: 13,744,000

(Photo credit should read Feature China / Barcroft Images / Barcroft Media via Getty Images)

15. Istanbul, Turkey

2016 population: 14,365,000

(Photo by Chris McGrath/Getty Images)

14. Calcutta, India

2016 population: 14,980,000

(Photo by NurPhoto/NurPhoto via Getty Images)

13. Buenos Aires, Argentina

2016 population: 15,334,000

(Photo by Pool ROSITO/WOLLMANN/Gamma-Rapho via Getty Images)

12. Karachi, Pakistan

2016 population: 17,121,000

(Photo credit should read RIZWAN TABASSUM/AFP/Getty Images)

11. Dhaka, Bangladesh

2016 population: 18,237,000

(Photo by Probal Rashid/LightRocket via Getty Images)

10. New York-Newark, USA

2016 population: 18,604,000

(Photo via Getty Images)

9. Cairo, Egypt

2016 population: 19,128,000

(Photo by Fayed El-Geziry/NurPhoto via Getty Images)

8. Osaka, Japan

2016 population: 20,337,000

(Photo by Eye Ubiquitous/UIG via Getty Images)

7. Mexico City, Mexico

2016 population: 21,157,000

(Photo by Brett Gundlock/Bloomberg via Getty Images)

6. Beijing, China

2016 population: 21,240,000

(Photo by Kevin Frayer/Getty Images)

5. Sao Paulo, Brazil

2016 population: 21,297,000

(Photo by Marivaldo Oliveira/Pacific Press/LightRocket via Getty Images)

4. Mumbai, India

2016 population: 21,357,000

(Photo by Satish Bate/Hindustan Times via Getty Images)

3. Shanghai, China

2016 population: 24,484,000

(Photo via Getty Images)

2. Delhi, India

2016 population: 26,454,000

(Photo via Getty Images)

1. Tokyo, Japan

2016 population: 38,140,000

(Photo via Getty Images)

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