The Penrose Staircase is a famous illusion which, like the tribar, was developed by Roger Penrose as a child with the help of his father. It is not often realized, however, that it is actually possible to construct the staircase. One famous version was made from Lego blocks. To see how impossible the construction should be, note that if you follow the staircase shown on the left in a clockwise direction you will always be descending, yet return to your starting point. In the version at right, if you follow the path clockwise, you will always be ascending, yet return to your starting point. Clearly this should be impossible for a real, three-dimensional object. But remember what we learned about the Penrose tribar! You should be able to construct a staircase that, viewed from one specific point, appears to be a Penrose staircase. Can you figure out how to do it? [If the staircase looks familiar to you, you have probably seen one of several different versions done by the famous artist M. C. Escher.]

How about a beautiful animation of a ball perpetually bouncing down the staircase? Lovely. And how about the large lego model below?

Click on the Lego photo for more information. Give up on how to do it? Click here. And here you can download paper models to cut and assemble of three impossible objects, including the staircase.