The world population
has grown to over seven billion people, and more people are living in large cities
than ever before.
People
look for jobs in big cities because they have more businesses, ports,
transportation, and educational institutes.
As
more people move into cities, the land prices rise, and taller
buildings are constructed to accommodate new residents and businesses.
New systems are required to provide services, such as water, electricity, and trash collection and
disposal to cope with the increasing population.
Also,
traffic and air pollution
problems caused by the increased number of cars on the streets have to
be dealt with.
As
more people live and work in large cities, these growing problems need to be solved.