Urbanization – the spatial concentration of people and economic activity·is arguably the most important social transformation in the history of civilization since man changed from being a nomadic hunter-gatherer and adopted a settled, subsistence agricultural way of life. While the timing and speed of urbanization have varied and varied between countries, regions, and continents, the urbanization process has taken hold everywhere. It has proven to be an unstoppable and mostly desirable phenomenon. Cities are the foundation of modern civilization; they are the engine room of economic growth and the centers of culture, entertainment, innovation, education, knowledge, and political power.

While the antecedents of urbanization are long, contemporary urbanization is now predominantly a developing-country phenomenon, centered largely in Asia. Urbanization in Asia involves around 44 million people being added to the population of cities every year. To put this in perspective, each day a further 120,000 people are added to the populations of Asian cities, requiring the construction of more than 20,000 new dwellings, 250 kilometers (km) of new roads, and additional infrastructure to supply more than six megaliters of potable water.