Big cities are wonderful places to live in.There are many nice things to see and to do.You can go to different museums and theatres.You can also go shopping to buy things from all over the world.
But there are many problems in big cities，too.The cost（费用）of living is high.And there are too many people in some places.Every year many people move to the cities because they want to find jobs or to study at good schools.But sometimes these people can't find good places to live in.Also，too many people in a small space makes it hard to keep the cities safe and clean.
