An Image Map Shader masks the large scale Power Fractal terrain to carve out the pass. A couple of Redirect Shaders (both on X and Z) at different feature scales give the cliffs bulge and bump. I utilised the Soft Shadows option to soften the shadow edges of the right-side cliffs falling on the left-side cliffs. It added 40% to the render time, but was worth it.
ps. I don't know if there is a pass at Arabah, which is near Petra, but why not.
John
