Yes, I used learning and fun in the same phrase.  The Franklin Institute in Philadelphia is a hot spot for school field trips and visitors of all ages because they do exactly that.  They make learning fun. 

There are several permanent exhibits to explore.  You can take a walk through a model human heart in The Giant Heart exhibit.  Space Command lets you learn about space and space exploration.  Learn all about trains and take a ride in a Baldwin 6000 at The Train Factory.  Other exhibits teach about electricity, air flight and more!  Also be sure to check out the nations second oldest Planetarium, an IMAX theater and the many traveling exhibits. 

If you've never been, I highly recommend taking the trip over the bridge.  It's located right in Center City at the corner of 20th St and Ben Franklin Pkwy.  If you take the Ben Franklin Bridge - Take 676 West. Exit at the "Ben Franklin Parkway/Museum Area" exit. At the top of the exit ramp, all traffic must turn right onto 22nd Street. One block later, turn right onto the Ben Franklin Parkway. Stay in the far right hand lanes. One block later, turn right onto 21st Street. One block later, 21st Street intersects with Winter Street. Just past the intersection, the entrance to the parking garage is on your left hand side.