cities of future

The growth of cities is inevitable. Nowadays, most of population in highly-developed countries is concentrated in cities with a very small number of people living in the countryside. The tendency is that the urban areas are get bigger and bigger with their population growing and the flow of people from countryside to big cities is unlikely to stop.
In fact, it wasn’t like that in the past. Until about XIX century vast majority of people lived in rural areas and massive migration to cities started along with the industrial revolution and continued with its progress. The main reason for that migration was generally similar to what it is today - search for employment that the countryside couldn’t provide for growing number of people. It was due to the advance in technologies that made working in the farms more efficient thus requiring less labour.
This trend, in overall shape, has continued to this day. People still move from countryside to big towns, however, the reasons for their decisions might be slightly different. Without doubt cities seem to be very attractive for young people and provide better opportunities not only in terms of employment and education but also in such fields as culture and entertainment. For many rural inhabitants big cites appear to be places where life is easier with better access to schools and hospitals.
However, a movement in the opposite direction can also be noticed. There are those who decide to abandon the big city life and choose tranquil countryside as their place of habitation. Yet the people who do that are usually affluent enough to afford it and in this case, it can be perceived as something extravagant by the poor who continue to move to big cities in search for better life.
It seems that nothing can change the process of big cities expanding and gradually turning into large metropolis and the countryside getting depopulated. However, the future is unpredictable. We might witness some kind of a drastic change that will prompt a massive migration from cities to rural areas. It may be that the pollution will reach such a degree that it will make urban areas unsuitable to inhabit or something significant like a global disasters, nuclear war or an outburst of a horrific disease will cause a major escape to the countryside and mother nature.