This is a 3D image of sand dunes in a martian volcanic caldera. It was made from two different MOC Narrow Angle images (with a resolution of ~7 meters per pixel) that covered the same set of dunes.
 
The dunes are barchans. Their steep, arcuate avalanching slipfaces on the lower left sides indicate that the wind blows from the upper right (from the northeast). The dunes are blowing across a cratered volcanic surface at the top of a volcano in Syrtis Major, Mars. The caldera at the top of the volcano is called Nili Patera. (Use red/blue glasses to get the whole effect.)