If you've arrived from elsewhere, hit this link . A doublet ridge is one of the many names given to the surface features on Europa. Arthur C. Clarke has even suggested that these new pictures look like a freeway system, so it's natural to use them as roads in the story.
North is to the top, and the sun is illuminating the terrain from the right.
Note that one ridge has been sheared by a right-lateral fault. Here's a 3-D view. Check out the picture here .