Jim Denevan carves enormous art pieces in the sand of deserts and beaches.  On a canvas that nature is prepared to wipe clean with wind or water the moment it’s been filled, he creates artwork so large it can only be appreciated from the air (at least in a lot of cases).

One basic example is this pattern on a beach with a tiny person poised in the center:

Other pieces are abstract, simple, or just daunting.  My favorite has to be this one.