Independence National Historic Park: Is home to Philadelphia's most important and historic tourist attractions, including the Liberty Bell, Independence Hall, and Congress Hall. Numerous historic buildings line the cobbled streets and provide insight into some of America's early history.
The liberty bell: Has long been a symbol of freedom and independence in the United States. It went on tour around the country in the late 19th C in an effort to inspire a sense of freedom and conquer divisions left by the Civil War. The bell completed its journey in Philadelphia in 1915, where it has remained.
The Philadelphia City Center: Is home to some interesting areas and sites, both old and new. The main attractions are the landmark City Hall with its outstanding Gothic tower, the Pennsylvania Academy of Fine Arts Museum, along with a modest Chinatown and numerous other architectural delights.
The Philadelphia Museum of Art: Contains one of the United States largest collections of art. It is housed in a neoclassical building fronted by a broad set of stairs which became famous after their use in the well know American "Rocky" films.
Source: http://www.planetware.com/tourist-attractions-/philadelphia-us-pa-phila.htm