It is no secret that cardboard boxes can provide all kinds of inexpensive fun for babies and toddlers, but you may as well make it look pretty like this DIY cardboard playhouse. The geometric dome is made by piecing lots of triangular cardboard boxes together. The electric blue tape is both functional and a cool design element.
From the blog Hannah and Lily, the DIY cardboard playhouse required larger boxes be cut down to form equilateral and isosceles triangles with folded edges. They were hot glue gunned together to form pentagons, which fit together to make one large igloo-like house. You can then place whatever fun toys and blankets inside.
For more crafty fun, you could also have your little one decorate the triangles before building with them or creating your own designs.