范文：Nowadays, the maps of cities are updated frequently. With the development of city, more and more suburbs become parts of the city. When the cities in the world are amplifying constantly, people discuss the topic hotly, the causes and consequence of the enormous cities. Different people have different answers by their respective views.

　　In my opinion, the evolution of society and the development of economy result in the growth of the vast size of cities. Since the number of population in every city is increasing continually, people need a large amount of space to live in. With the progress of the technology, the output of crops rises sharply. Fewer and fewer farmers are required, as a result, more and more villages urbanize. The growth of the cities brings us many huge changes.

　　There are more job opportunities in the cities. For instance, China will hold the Olympic Games in Beijing in 1008. The government is amplifying the size of Beijing to build new gyms in order to hold it excellently. Obviously, people in the cities could gain a lot of new jobs.

　　Of course, the enormous size of cities also has bad effects. Pollution is becoming more and more serious all over the world with the amplification of the cities. For example, the poisonous gas sent off by factories and automobiles has made the air unhealthy for people to breathe. Water waste keeps pouring into rivers and lakes; as a result, many water species are dying out. Furthermore, more people the city have, more rubbish we can find.

　　In a word, since each coin has two sides, we should be acquainted clearly with the reasons why the size of the cities has grown enormously and what it will bring us. Thus, we could make full use of the positive effects and overcome the negative effects.