Los Angeles-based tinkerer, Ben Tardif, has spent the last three years of his free time constructing this amazing marble obstacle course, which he's named Marble Mountain. The mountain, which is still a work in progress, has many different sections, including a ski jump, roller coaster, and a skate park. You can follow the progress of Marble Mountain on Instagram.
"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. 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."[Ben Tardif]