Down the rabbit-hole
This tessellation consists of concentric square twists of growing size. The medium is self-adhesive holographic foil glued onto tracing paper. The spiral is a fractal and with larger paper could be extended indefinitely with more and more levels.
Just after I designed this piece, I realized it was so simple that someone had probably invented it before. After a bit of searching on flickr, I realized I had just designed from scratch a tessellation almost identical to the Hill/Bump model by Matt Humberstone which I had seen on flickr and faved just a few days before. It’s disappointing when what you thought was an original design shows to have been designed by others a few years before. The only difference is that in my model the initial twist is based on a 2:1 slope and Matt’s starts with a 3:1 slope. As a consequence, my version should be folded from an odd-numbered grid (the one in the picture is from 25×25 grid including an extra-wide frame). My model also lacks the locks holding the model together in the corners because it was designed up-front to be viewed from the “tunnel” and not from the “hill” side. Since it was designed to be flat, there are small additional creases that prevent it from bulging upwards. Apart from these small differences, you can use the same crease pattern as for Matt’s version.