Cool image time! In the past few days the Themis camera on Mars Odyssey has taken two pictures of the vast Olympia Undae dune field near Mars’s north pole. The image to the right is only a cropped, lower resolution section of one of those images.
The image was taken during the summer, so most of the winter CO2 frost has sublimated away. Unfortunately, the website does not provide a scale, though they say the full images each cover about 12 by 43 miles of territory. Yet, both images capture only very tiny portions of the dune field, which apparently goes on and on for many hundreds of miles in all directions, looking exactly the same wherever you look.
Just imagine trying to travel though this area. It is the epitome of a trackless waste. And without some form of GPS system getting lost forever would be incredibly easy.