Xtreme Zipline at Utah Olympic Park!!! Experience what it's like to be an Olympian flying off the K120 nordic ski jumps on our Xtreme zipline. The Xtreme Zipline is like our K120 jump - big, steep and long. In fact, the Xtreme is the steepest zipline in the world. Your ride starts at the edge the K120 jump, at which point the force of gravity takes over and propels you to 50 mph, which is fairly close to the speeds of world-class ski jumpers.