Earth in the palm of your hands. Mess with Earth till it looks exactly the same as before. :-)
Based on Emmetts screwless Heartgear: http://www.thingiverse.com/thing:12208and the textured earth by bld:http://www.thingiverse.com/thing:17336
Takes one revolution till it is back to normal. Size is 140mm in diameter.
Good luck with the assembly, it's quite tricky. ;-)
Earth Gears by hachiroku is licensed under theCreative Commons - Attribution - Share Alikelicense.