Photo-montage
Lennard Verjans (lonzard)
Here, we see Penrose tribar above mounains.
Behind the triangle are complex curves, which can be made by playing with Spirograph.
Artist's deviantART profile http://lonzard.deviantart.com.
The image was found at http://lonzard.deviantart.com/art/Penrose-Triangle-177512085