Edgar Allen Poe house. Betsy Ross house. The Constitution Center. Independence Hall. The Philadelphia Mint is right there, as well. If you like to see neighborhoods, walk through the streets a few blocks south of Independence Hall—the Society Hill neighborhood.
The Franklin museum is a great technology museum. The art museum is having a very cool Calder jewelry exhinit now over in the new building. 2nd and 3rd Streets north of Spring Garden Ave (Northern Liberties) for a lot of funky restaurants (Standard Tap, if you want a selection of a gazillion beers) has really great bar food.
Take a carriage ride, but just know that not every historical story you hear may be accurate. There’s also the Duck, which is another way of touring both land and water. Please don’t squawk your duck whistle too loudly. It’s really annoying.
Cheesesteaks are overrated, and the best ones are at Pat (Olivieri’s) King of Steaks in the Reading Terminal Market (which is another wonderful place to visit), if they are still open (they’ve being kicked out by Tony Lukes—long story).
All right, that’s more than a couple days worth. Have fun. It’s a nice place to visit, but it’s an even better place to live!