This Persian rug is made of colored sand and is located beside the Straight of Hormuz. Life In The Fast Lane has some great images of the "carpet" being assembled as well as some largest sand carpets of the past and some neat sand sculptures.
http://www.lifeinthefastlane.ca/worlds-largest-sand-carpet-and-intriguing-sand-art/art
When I see things like this, it always makes me marvel at the brain.
I mean to think that people could put this together! Mankind is truly magnificent.