There are many big cities in the U.S.A. , but just a few are interesting enough to be distinguished. Philadelphia (in state of Pennsylvania) is one of these, because of its historic district: an old part town that was partially preserved. Philadelphia is best known as the birthplace of the United States, a place where the US Constitution was signed. The Liberty Bell, Independence Hall, and Rocky Balboa (character from the Sylvester Stallone's 1976 movie Rocky) are not only symbols of the city, but also well known American icons.