Whirlwinds on Mars, From the Ground
Neil Halelamien writes "Back in 1999, satellite images were photographed of 5-mile-high whirlwinds streaking across the surface of Mars. A couple of months ago the Spirit rover got a close up view of whirlwind tracks, and this past week photographed a whirlwind in action (animation). It's thought that these dust devils may be responsible for the mystery power boost to the rovers' solar cells. Last year the rovers also spotted clouds and frost."
You can't see the Great Wall unless you got a real good zoom lens (radar don't count).
http://www.snopes.com/science/greatwal.htm