One of the activities that 3Po and Jammy enjoyed most during their week at Camp Galileo was building a suspension bridge out of pipe cleaners, wood, cardboard and rocks. It wasn't just a beautiful art project: the bridge actually had to support the weight of 100 pennies! It was exactly the kind of challenge they relish. Even more important, they applied and learned some important engineering principles: forces, weight distribution, counterbalancing, etc -- have stuck with them. Now they know the difference between a cantilever and a suspension bridge, and every time we cross the Bay Bridge or the Golden Gate Bridge, they can look at the structure and understand what the trusses and cables are for.
Those lessons have definitely stuck with them: one afternoon a couple of months ago I found myself browsing through the Galileo Learning blog and came across a post describing a Gumdrop Bridge Challenge. It was a slow afternoon, and I already had toothpicks and mini marshmallows in the cupboard, so I challenged the boys to build a 10-inch bridge with just 40 toothpicks and 20 gumdrops.