It is one of the greatest challenges that humanity will have to overcome in the years ahead.  According to the United Nations, by 2050, two out of every three humans will live in an urban area.  Twice the current number, or an additional 2.5 billion people.  Urbanization is growing at an unprecedented rate, particularly in the cities of the Global South.  In Africa, the urban population is due to increase by 91% in 25 years, reaching 2.6 billion by 2050.  In Asia and South America it will rise from 2 billion to 4 billion.  This exhibition looks at the issues raised by this exponential growth in three megacities.