From Trash to Geometric Construction...
I recycled some plastic signage into a "slide-together" geometric construction. The whole structure is about 15 inches high and is pretty sturdy! It is made of 30 identical squares, with slits cut at certain locations.
If you want to make your own geometric construction, visit George W. Hart's website at www.georgehart.com, and find complete instructions, as well as many more models, there. Have fun!