I found this video called “Longest Marble Run In the World”: this guy just built a huge long marble track around his house. 

It’s really is super long, about 492 feet long, but I don’t know that it's the longest in the world. I would want to see something from the Guinness Book of World Records to be sure. 

But even if it's not the longest in the world, I was totally into watching this little marble fly all around. Scott, the guy who set it up, really had some creativity with ramps and jumps and elevators!