The social role of the city

As well as being the seats of power, wealth and knowledge, cities
have also been catalysts for social change and revolution. 

They have been the source of most of the enduring changes that underpin human freedoms including the development of politics  (from the Greek word polis meaning city), the centre of revolutions that have
 helped to shape the modern world and the struggles for human rights. 
Arguably cities are the birthplace of democracy which, we would argue, is a vital feature of
sustainability. 
The essence of cities is The essence of cities is that they have always contained a myriad of diverse and intense connections and activities; where people live, work, shop and play, meeting the needs of economic
production and social reproduction (Smith, 2002). 
They bring together people from many different backgrounds and cultures.
This can be purely in terms of physical proximity but also in the creation of space for fusing ideas, styles and activities. 
They are centres for many cultural forms. Without romanticizing theirhistory, which has its grim share of oppression, hunger, crime and pollution, cities have been the driving force for innovation, social improvement, cultural activity and diversity