You kind of have to watch to see what it's all about. This little Rube Goldberg-esque machine, takes its steel marble passenger up to the top of the tower using only gravity and a few other natural little tricks. It's all hand-built and seems to be the third built by its creator, who says at the end of the video that there is still some work to be done on it.
And the fun isn't over once it reaches the top (well, it is in the video, but hey) — the machine is good to go as soon as the marble gets to the peak; it can be delivered to the bottom again and will run for 24 hours straight, limited only by the potential energy of a single large weight used to reset some of the mechanisms. Wish I had the time (and skill, and space, and wood) to build something like this.