The population is growing at an alarming rate. By 2050, there will be almost 10 billion people on the planet and the majority of the world's megacities will be in Asia.
According to environmentalists and urban planning experts, Dhaka, one of the most crowded cities in South Asia, has already started feeling the heat of an overcrowded populace with problems like traffic jam and water-logging.
Based on population growth models, the Global Cities Institute at the University of Toronto projects that Dhaka, the capital of Bangladesh, will be the third most populous city in 2050 with about 35.2 million residents.
These will be the 10 biggest cities in 2050
1. Mumbai, India: 42.4 million people
Devotees try to form a human pyramid to break a clay pot containing curd during the celebrations to mark the Hindu festival of Janmashtami in Mumbai on August 10, 2012.
Mumbai will not be No. 1 for long.
The Global Cities Institute projects that Kinshasa, in the Democratic Republic of the Congo, will be the most populous city in the world by 2075, and that by 2100, it will be surpassed by the 88 million future residents of Lagos, Nigeria.
2. Delhi, India: 36.2 million people
India's Prime Minister Narendra Modi performs yoga with others to mark the International Day of Yoga, in New Delhi, India on June 21, 2015.
3. Dhaka, Bangladesh: 35.2 million people
People crowd on top of a train entering the Dhaka airport rail station September 24, 2015, as thousands of Bangladeshi Muslims head home to celebrate Eid-al-Adha.
4. Kinshasa, Democratic Republic of the Congo: 35 million people
Fans climb a scoreboard to watch an African Cup of Nations qualifying soccer match between Ivory Coast and Democratic Republic of Congo in Kinshasa on October 11, 2014.
5. Kolkata, India: 33 million people
Hindu devotees prepare to receive rice as offerings being distributed by the temple authority on the occasion of the 'Annakut' festival in Kolkata, India on October 24, 2014.
6. Lagos, Nigeria: 32.6 million people
People crowd on a road near Balogun market to shop, a day before Christmas in Nigeria's commercial capital Lagos December 24, 2012.
7. Tokyo, Japan: 32.6 million people
Runners fill the street at the start of the Tokyo Marathon in Tokyo February 22, 2015.
8. Karachi, Pakistan: 31.7 million people
Supporters of the political party Pakistan Tehreek-e-Insaf take part in a rally near the mausoleum of Mohammad Ali Jinnah in Karachi, Pakistan on December 25, 2011.
9. New York, United States: 24.8 million people
Revelers take part in New Year celebrations in New York's Times Square January 1, 2010.
10. Mexico City, Mexico: 24.3 million people
Pope Francis arrives in the popemobile for meeting with families at "Victor Manuel Reyna" stadium in Tuxtla Gutierrez, Mexico, February 15, 2016.
