UFOs are often accused for creating amazing and apparently impossible to be made by a human crop circles and mazes but I personally do believe that all of the crop circles and mazes you have seen until today were exclusively made by humans.
If you really thought that only UFOs are able to make amazing crop circles and mazes you should see this interesting competition organized by NASA. Seven farms were included in this competition. Every competitor, i.e. the owner of a corn field who decided to participate in this competition, had to make an unique corn maze dedicated to presenting achievements of NASA until now.
So here you can see the seven cornfields with the mazes that were designed by company called The MAiZE which is specialized in designing cornfield mazes.
For more information on participating farms, visit Space Farm 7.