Scientific American magazine rated the Exploratorium "the best science museum in the world" -- pretty heady stuff for this exciting hands-on science fair. It contains more than 650 permanent exhibits that explore everything from giant-bubble blowing to Einstein's theory of relativity. It's like a mad scientist's penny arcade, an educational fun house, and an experimental laboratory, all rolled into one. Touch a tornado, shape a glowing electrical current, finger-paint using a computer, or take a sensory journey in total darkness in the Tactile Dome -- you could spend all day here and still not see everything. Every exhibit at the Exploratorium is designed to be interactive, educational, safe and, most importantly, fun. And don't think it's just for kids; parents inevitably end up being the most reluctant to leave. On the way out, be sure to stop in the wonderful gift store, which is chock-full of affordable brain candy.

The museum is in the Marina District at the beautiful Palace of Fine Arts, the only building left standing from the Panama-Pacific Exposition of 1915. The adjoining park and lagoon -- the perfect place for an afternoon picnic -- is home to ducks, swans, seagulls, and grouchy geese, so bring bread.