A couple more - just walking around the Old City/ Society Hill between Market and South, Broad to the Delaware, is worth the time and effort. Lots and lots of lovingly restored old buildings and historical markers everywhere. You name the Revolutionary Era history event and there's something that happened in Philly to go with it. Half streets and quarter streets just wide enough for a one-horse wagon. Betsy Ross' house. Add the Barnes Foundation collection (in its, grr, new home) to the list of museums. Also see if there's anything at Symphony Hall (right next to the Union League Clubhouse - nice architecture).
It's a great city for just walking - one of the best in America in that regard.
If you go, do make a point of seeing the Olympia b/c there's talk of scrapping her as she's just deterioriating to nothing.
Also, if you want to get out into the green, go up the Schuylkill past the boathouses into Wissahickon Park and to the Arboretum. The Chestnut Hill neighborhood is a nice one for walking, too, though it's more residential and less dense than Old City/Society Hill.
Also, the Phils ballpark is a very nice place to see a game and you can take the subway to the game.
One could spend a week there and not see it all.
And have some Italian Ice. You'll need it to cool off.
One more thing - 30th Street station - where Amtrak stops, used to be part of the Pennsylvania RR. Beautiful old building. And the memorial statue to those employees of the PRR who died in WWII will break your heart.
Last edited by Dave in Maine; 06/14/12 06:49 PM.