Ok, I can't take credit for doing this craft but I'd like to think I could pull it off as well. My mother took some cardboard boxes, including a large freezer box, and turned them into very cool castles. She put these together for our daughter's third birthday party, but this is a fun thing to do anytime.

We had just bought a freezer so a large box was easy to get but you might be able to get one from a local appliance store or freecycle. My mom cut the top of the boxes to resemble the top of a turret and used leftover contact paper to cover the outside to make them look nicer. You could also try wallpaper, construction paper or leaving it plain and just draw "bricks" or allow the kids to color it in.

The larger castle (left photo) had a door and window cut out, making it a lot more fun for pretend play. On the smaller castle (middle & right photos), she cut out the front because the box was too small for a door.

She embellished the larger castle with a beautifully stenciled sticker "Once Upon a Time There Was a Princess..." Because these castles were for a birthday party, we added another element. We had stickers and markers and let the guests decorate them.

There were a little bit of work to create but you can put together a simpler castle that would still be tons of fun and they last a long time. My daughter's birthday party as mid-May and as of mid-July they are all still actively used and holding up well (although the smaller ones are a little creased). So it's well worth the effort.