There is something COOL about boxes. They spark imagination in amazing ways. I remember my dad bringing home boxes from work. What he planned to do with them is beyond me. It just dawned on me that he probably used them when he separated from my mom. My brother and I were oblivious. Those boxes were an incredible draw for our curious minds. We pulled them out to the front porch stacking them up to make the best fort ever - complete with a window.
A large box would have been awesome as well. Here Ian took up residence, literally, in a box.
You can see he taped a steering wheel inside the box. I also allowed him to color the outside of the box - he opted for a car theme. It survived several days as his brother and sister pushed him around the livingroom so he could drive. He begged to eat dinner in it, "driving" by the kitchen as if it were a fast food restaurant. He would push stuffed animals around in it and finally he tucked himself into the box to pretend sleep, only to really fall asleep.
Eventually it collapsed and was escorted to the trash. Other boxes came to life under Ian's command, but I don't have pictures of those.
Yes, a cardboard box is the BEST TOY EVER!