This is the Citadel, a massive K'nex ball moving machine built by Youtuber Shadowman over the past three years (previously: his functional K'Nex Skeeball machine). In Shadowman's own words while I harness the power of a dozen suns and turn everybody into a shadowman so he's not alone.
This machine features more than 45 new elements, 5 different lifts, and 2 new path separators that separate into 17 paths. It's also themed, with Knex men all over the place working on it, giving it a factory-type feel with catwalks and stairs. There are 3 total motors, one of which powers all 3 floor lifts. The actual time it took to build is one year, there was just a long break in between. All of the paths (except one) were built in 6 months, starting in December 2015.
Such engineering. It's amazing people build stuff like this, and it's even more amazing they have the space to keep it. This thing looks like it has its own room. I don't even have my own room and I'm a human being. My mom makes me share a room with my big brother. "No, he insists on it because he's afraid of ghosts." Mom! "If he pees the bed he has to wash the sheets himself." Stop!
Keep going for a video detailing all the different paths.
Thanks to Gregory C, who moves balls the old fashioned way: shaking your leg so they stop sticking to your thigh then casually readjusting.