This one takes place on Machu Picchu.
At checkpoint 6 you'll jump to a large physics ramp. Ride to the top of that ramp and stop. Roll back down, controlling the angle of descent and you'll find a secret area. Get to the back of that secret area and wait on the pressure plate you'll find, until you're bathed in a green light.
Once that's done, ride to the end of the track as normal. Just before the finish line a green light will be waiting to abduct you.
You'll be teleported to a short track, with checkpoints, where your bike is attracted to green lit objects. Ride to the end of this track, through an awaiting squirrel, and you'll find yourself floating in space. The achievement will then unlock.