In this photograph taken on June 29, 2014, passengers cross a footbridge at a railway station in New Delhi.
Delhi has become the world's second most populous city in 2014 after Tokyo, more than doubling its population since 1990 to 25 million, according to a UN report.
The 2014 revision of the World Urbanisation Prospects launched yesterday said that India is projected to add the highest number of people to its urban population by 2050, ahead of China.
The Indian capital is expected to retain the spot of the world's second most populous city through at least 2030, when its population is expected to rise swiftly to 36 million.
Tokyo topped UN's ranking of the most populous cities in 2014 with 38 million inhabitants and while its population is projected to decline, it will remain the world's largest city in 2030 with 37 million people.
Mumbai, which ranks sixth on the list of the world's most populous cities in 2014, is projected to become the fourth largest city in 2030 when its population would grow to 28 million from the current 21 million.
Tokyo and New Delhi were followed by Shanghai with 23 million, and Mexico City, Mumbai and Sao Paulo, each with around 21 million inhabitants in 2014.
The report said that the largest urban growth will take place in India, China and Nigeria between 2014 and 2050, with the three countries accounting for 37 per cent of the projected growth of the world's urban population.
By 2050, India is projected to add 404 million urban dwellers, way more than China's projection of 292 million.
Nigeria will add 212 million to its urban population.
India's current urban population is 410 million people and this will grow to 814 million by 2050.
China currently has the largest urban population of 758 million.
India and China account for 30 per cent of the world's urban population.
The two Asian giants along with the United States, Brazil, Indonesia, Japan and Russia currently account for more than half of the world's urban population.
About 54 per cent of the world's population currently lives in urban areas and this proportion is expected to increase to 66 per cent by 2050, with the maximum increase taking place in the urban areas of Africa and Asia.
The world's urban population is now close to 3.9 billion and is expected to reach 6.3 billion in 2050, according to the UN report.
The rural population of the world has grown slowly since 1950 and is expected to reach its peak in a few years.
Approximately 3.4 billion people currently live in rural areas around the world.
However, sometime after 2020, the world's rural population will start to decline and is expected to reach 3.2 billion in 2050.
India currently has the largest rural population at 857 million, followed by China (635 million).