One thing I've noticed over the years is that no matter what we give our son for a present, what he often plays with the longest is the box the gift came in. He is now 12 years old and he still loves boxes and building with them. I work for a toy company and they often ship displays to our house. As soon as Benjamin sees them, he immediately responds, "I get the boxes!"
Once, when my wife was out of town, he and I took quite a few very large boxes, opened them up, and made a maze in our living room (once we had moved all the furniture out of the way). We would take turns blindfolding each other and then whoever was blindfolded would try to find their way through it. Sometimes we would change the maze while the other person was inside of it just to make the maze more complicated. My son loved doing that and often laments that we don't have those boxes to build mazes out of anymore.
We have made houses, forts (including one that whoever was in would shoot Nerf darts at the attacking force and the other would have to dodge the darts), castles and puppet theaters out of boxes. The possibilities were endless as were the hours of fun we had. It's like that episode of Spongebob where he and Patrick get inside of a box and use their imagination to create all sorts of things and noises. Poor Squidward is baffled by what he views as their nonsense, though he desperately wants to understand how they do it.
How many kids are like Squidward and don't get it? How many of them miss all of that because they are seated in front of their computers or game systems? I can't help but see how limited too many kids are in their imaginations because they have so many things to entertain them that yet complain often that they're "bored."
When I was a kid, we spent most of our time outside, playing in the woods, and making up our own games. With two pieces of rope, we would play "Jump the creek" where we would all take turns jumping over the distance of the two pieces of rope and would move them further and further apart. My friends and I would often put on our own "shows" to entertain ourselves. And, like my son, I used to love playing in boxes as well (see photo below).
I want for him to unplug from his computer or the TV or video games and I try to encourage him in his love for playing outdoors. My wife and I often take him out to nearby mountains and creeks to go hiking and exploring. One thing he and I like to do is to find river rocks and make small dams (replacing the rocks where we found them when we're done).
There will come a day when he won't want to play in boxes anymore but he'll get to relive those earlier moments when he has kids of his own and he sees how much they prefer the boxes.