Wow- where was this when GIANT cardboard boxes were common place. I remember building elaborate forts in my backyard from refrigerator boxes.. and making plans to “live” there indefinitely and BEGGING my parents to let me sleep there overnight. I even remember rigging up electricity and putting lights in one of them .

This is VERY cool- the site has plan for making your own cardboard castle. They are very well thought out elaborate and in my mind this is the quintessential homeschooling project. The kit includes Rivets , knife for cutting and plans.

http://www.mrmcgroovys.com/p-13-cardboard-castle-kit.aspx