From the main menu, select "Create". Once in the world, go to the following position on the world map:
Now, select a start point and an end point for the track. Now create a "New Object", and select "Environments" > "Terrain". Once selected, use "Edit Properties", and make sure the object is a Hole, Crater 5, and that Decal is off.
Now, use the "Copy" function to repeatedly take chunks out of the top of the mountain peak until you unveil the key. The exact location can be seen in the video.
*Posting for Maka91, because he is only playing the Xbox One version.