Firstly there's Independence Hall where both the Declaration of Independence and the U.S. Constitution were signed. You can see the LIberty Bell for free but have to stand in a long queue which actually goes quite quickly.
There's a visitor's centre which is very informative and has some great staff to help.
There are some great hotels nearby at Penn's Landing where there's a nice walk along the Delaware River. The Hilton Philadelphia is a high-rise waterfront hotel. The vibrant Old City District and charming Society Hill neighborhood are within walking distance. The hotel is just a few blocks from Philadelphia's historic attractions such as the Liberty Bell, Independence Hall, Betsy Ross House, and the National Constitution Center.
Run up the steps like Rocky in the movie or get your photo taken with the bronze Rocky statue which Sylvester Stalone dedicated to the city after the movie.