In July of 2010 Skyler was three months shy of 2 years old and I was just shy of my due date for Julia. We were getting ready to sell our beach cottage and were in full HGTV mode beautifying our home which included buying a new grill for the deck. Since we were busy getting things ready for a new baby and a new home I don't remember doing much grilling, but I do remember the house we made for Skyler with the box from the grill. It was a rainy day on the weekend and the 3 of us spent all day on it.
By the end the house had windows, a flower box, an awning, a light, a door handle and a mail slot. It was fully wallpapered on the inside and the outside was "painted" with crayon. The best feature for Skyler, by far, was the mail slot.
The house made it through the move and into our rental house where it spent the next year and a half. It was the most used "toy" that we had. Even the cat enjoyed laying on the rug inside. Seven years later boxes are still in high demand. The girls spend hours getting them designed just as they want to create houses with multiple rooms, sleds for their dolls, and homes for their stuffed animals.
If you're looking for a summer activity try a cardboard box creation and let me know how it goes!