Reasons to go to Philadelphia: Great museums, great (cheap, thanks to widespread BYOB restaurants) dining, and real historical significance. Philly can be rough, though-- it is (believe it or not) the 5th largest city in the US, and you will be able to find urban blight if you look for it. Philly must-sees include the Museum of Art, the Constitution Museum, and Independence Hall. May people like the main line suburbs, but I'm not as sold on them unless visiting friends or the many colleges  more...