"Marble Mountain is a large marble machine still under construction. It consists of 25 sections that mesh together to form one kinetic sculpture. Every element is themed (or will be upon completion) to an aspect of my life or to something that I find interesting. Some of the elements include a roller coaster, ski jump, Times Square, Lombard Street, and a skatepark. It took 3 years to get to this point of being able to turn it on and watch it go, and I will continue to work on it and get it fully completed."More here. And discussion thread with the creator here.