We moved to Denver a few months back, and wound up with enough empty cardboard boxes to start our own Amazon distribution center.
The boxes were on their way to the recycling bin when inspiration struck: we could build an EPIC cardboard fort for our nephews.
Armed with our leftover packing tape we went to work building tunnels, periscopes, and secret passages.
When the boys came over to play we gave them each a flashlight, and unveiled the fort with a drumroll. We'll never forget the boys' excited screams as they explored the cardboard maze.
Even better than that... it held their attention for HOURS and their parents got to relax. When it was time for the boys to go home they were both snoring softly.