Arthur Ganson has a sculpture at the MIT museum called "Machine In Concrete" that consists of a 12-stage geartrain, where each stage reduces the speed of rotation by a factor of 50. The left end is spinning furiously at around 200 rpm; the right end is embedded in a concrete block. The end in the concrete makes one revolution every 2 trillion years or so.
Here is a partial picture of the machine from Ganson's own website:
http://www.arthurganson.com/pages/sc...te%20page.html
But to really appreciate it, you can see a video of the sculpture (and Ganson's comments about it) at the 8:30 mark in this video from the 2004 TED conference:
http://www.ted.com/index.php/talks/a...sculpture.html