The World's Ten Biggest Metropolitan Areas

5. Mumbai, India
Metropolitan area: 21 million people
City: 13 million people

Mumbai – known as Bombay until the name was officially changed in 1995 – is the most densely populated city in the world. Through high birth rates and a perpetual influx of migrants, Mumbai’s population is expected to grow by one fifth in the next ten years.

Urban Detail:
Over half of the city’s population is still living in slums. Poor infrastructure and widespread poverty make it very difficult to meet the demands of an ever-growing population. (Photo: Reuters)