Last entry, I mentioned that I once contemplated building a Linka model of M. C. Escher's Relativity. I never actually did that, but I did put together a neat study model of the scene, out of folded graph paper (and a bit of cardboard for support). I've just posted a picture of it on my sculptures page.

If you're modeling this scene yourself, this picture could be a useful reference. It's pretty accurate, though perhaps not exact. (There's room for disagreement on some staircase widths, for instance.)