German artists Marion Ruthardt and Gregor Vosika created these amazing street art pieces for Nike's "I Run" campaign in Russia. Completed at four different parks in Moscow, the detailed murals give off the optical illusion that runners must overcome challenging obstacles in their path to get to the other side of the road. The frightening obstacles include: crossing over a large hole in the ground by balancing on a log, walking across a waterfall by crossing a suspension bridge, balancing on arctic glaciers, and passing through a river by skipping on rocks. The artists first used a special technique to sketch out the image on the asphalt with chalk, then they begin to paint it in. Each piece took them over eight hours to complete.