Andres Amador makes large, crop circle-like "paintings" in the sand on the beach at Ocean Beach in San Francisco, and at Burning Man.
Here is a gallery which plays a slide show that has controls for speed and image size.
And here is a (sadly all too small) QuickTime movie time-lapse of a sand circle being made.
Some spectacular imagery - and no crops were trampled on in the making...
Via Kevin Kelly