I just bought world machine and was wondering if anyone had some good ideas of how to make a vally with cliff faces on either side. All the cliffs I seem to make are not steep enough.
Once you make your basic cliff shape, try using a Transform (or a series of them) with high Canyonize and/or Glaciation settings. Of course if you have the registered version, you can just draw the shape you want with the Curves device. 
- Oshyan