What happen to people if they move to a big city?

If people move to a big city they have to adopt many changes. For example, there will be more noise and you might not be able to sleep. Also, there might be more criminals because they know that many people live there so there will be easy money. The following is an experience I had. Before visiting Washington D.C, I had expected it to be more crowded. While been there, I saw a lot of people in the streets. There were crosswalk signals that help people to be safe while they cross the streets. While walking on the streets, I felt insecure because there were too many beggars. And when I went to the museums, there were a lot of people there too. However, being at the museums I felt secure because the police was there. In another occasion I went to Mexico City and I felt insecure as well. Before visiting Mexico City, I knew that there are many robbers on the streets because my aunt lives there and she told me. Mexico City is dangerous because people steal everything you have when you walk in the streets. During a moment I was scared because a man followed us after we went to church. While being there I saw that in Mexico is always traffic, it does not matter the time.