When cliffs are viewed from the higher ground, if the lower ground is the same sort of terrain the edge of the cliff becomes obfuscated. This is a common problem in game development, and the usual solution is to mark the edge with a darker shading. Usually this darker shading is only visible when viewing from above. Allow me to demonstrate:
How it is:
How it should be:
Do you see how the grass in the second image has slight shading on the top left and top right edges? This helps to clearly mark the edge. One last thing: the shading will look best if it is only present on the top edges, not the bottom edges. If you also add shading to the bottom edges, you will get something like this:
...which looks gross.
There is a black outline on the cliff in hafen, but it is too subtle to really undo the effect.