1. Population density: The population density in big cities is very high, and there are too many people coming and going in the streets. This may not be suitable for early people from the countryside.

2. Traffic congestion: The traffic congestion in big cities is very high, and the traffic jam lasts for a long time. It's hard to imagine how much time is wasted driving in the city.

3. Development opportunities: Big cities have many development opportunities, many career choices and good income.

4. Health problems: Due to urban traffic and pollution, there may be more health problems, such as respiratory diseases.

5. Cultural activities: There are more cultural activities in big cities, such as exhibitions, performances and concerts. The intersection of multi-cultures can also enrich life experience.

6. High prices: The prices in big cities are relatively high, and food, rent, transportation and shopping will be more expensive.