A new UN report is forecasting that by 2030 two-thirds of the world's population will be living in cities.
At the same time, the urban population in developing countries will double and the area covered by cities could triple.
The report launched on Wednesday by UN-Habitat also says that in 15 years cities will by producing as much as 80 per cent of global GDP.
In the 20 years since the last UN conference on cities the report said the centre of gravity for “megacities” has shifted to developing regions.
In 1995, there were 22 large cities with between 5 and 10 million inhabitants and 14 megacities with more than 10 million, the report said.
By 2015, the numbers had doubled to 44 large cities and 29 megacities, most located in the developing world.