Founded more than 175 years ago to honor Benjamin Franklin, the institute is a science museum that is as clever as its namesake, thanks to an abundance of dazzling hands-on exhibits. To make the best use of your time, study the floor plan before exploring. You can sit in the cockpit of a T-33 jet trainer, trace the route of a corpuscle through the world's largest artificial heart (15,000 times life size), and ride to nowhere on a 350-ton Baldwin steam locomotive. You'll also find a working weather station, the world's largest pinball machine, and Franklin's famous lightning rod. One don't-miss: the 30-foot-tall statue of Franklin.

The Franklin Air Show celebrates powered flight with the Wright Model B Flyer. The Sports Challenge conveys the physics, physiology, and material science behind your favorite sport by simulating surfing, climbing a rock wall, and comparing your sneakers to Shaquille O'Neal's size 22s. The Fels Planetarium -- which has a state-of-the-art aluminum dome, lighting and sound systems, and a related astronomy exhibit, "Space Command" -- has shows about the stars, space exploration, comets, and other phenomena. The Mandell Center includes the Tuttleman IMAX Theater, with a 79-foot domed screen and a 56-speaker sound system; recent movies include Lewis & Clark: Great Journey West and Mystery of the Nile.