The Philadelphia Museum of Art is a must if you're in town. You could spend a whole day there! There are so many exhibits and things to see. I liked that they have restaurants inside, so you can take a break and enjoy a quick bite or a sit down meal.
I did not like the fact that the museum has been announcing Van Gogh's Sunflowers exhibit (the reason why we visited) just to find out it won't be open until May 18th! So if you're hoping to visit before then, be aware. The exhibit is still being finalized.
We really enjoyed the immersive exhibits, such as the Tea House, the Arts of the Islamic world, and the Arms and Armor. I had never seen such exhibits, so we really enjoyed it.