World Population Day: Top 10 World's Most populated cities in Pics

As the World Population Day is annually observed on July 11, this year India's two top cities Delhi and Mumbai have emerged in the list of world's most populous cities.

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.

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.

India is the second most populous country in the world and at the current rate of growth, the population of India is expected to surpass that of China by the year 2028.

The theme for this year's World Population Day chosen by the United Nations Population Fund (UNFPS) is "Investing in youth".

Here let's take a look at top 10 world's most populated cities:

Tokyo- 38 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.

Delhi- 25 million

Delhi, the national 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.

Shanghai - 23 million

Shanghai, the largest Chinese city is on number 3 with 23 million population.

Mexico City- 21 million

Mexico City has a population of around 21 million inhabitants in 2014.

Sao Paulo- Approximately 21 million

Sao Paulo is the largest city in Brazil with thepopulation of around 21 million urban inhabitants.

Mumbai - 21 million

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.

Osaka- Above 20 million

Osaka is a city in the Kansai region of Japan's main island of Honshu with the estimated population index of above 20 million people.

Beijing- Below 20 million

Beijing, the capital of China is on 8th number in the list of world's most populous cities with below 20 million people.

New York-Newark- 18.5 million

Newark, a village in Wayne County, New Yorkhas a population of around 18.5 million urban dwellers each.

Cairo- 18.5 million

Cairo, the capital of Egypt and the largest city in the Middle-East and Africa has a total population of around 18.5 million.