@ Istria- Dennis Oppenheimer is considered one of the founders of Earth art. He will always go down as a significant figure in land art history. His pieces can look like something straight out of the movie Beetle Juice. I have seen one of his pieces in person, and it was pretty spectacular. The piece is a house that is stretched out into a bus that coils into the ground. The piece is actually a functioning bus stop in Ventura, California, and it is about three or four stories tall. It is only fitting that this piece is in California, since he is a native.
He has another famous piece in a park in Vancouver that I would like to see one day. It is an upside down church built from aluminum and stained glass. The steeple is rooted into the earth. The piece is called "The Root of all Evil". It was originally on display at Stanford University (his Alma Matter), but it was taken down. I assume it was too controversial for the University.