Thanks guys
I wasn't so sure about the lighting, think the shadows are a tad too bright, but it seems you guys like it so maybe I've to try to look it in an other way.
Here's some info about how this is basically done:
The wall is a stretched heightfield (10000x1500m) with a "vertical adjust" shader attached to it and set to a couple of hundred metres. Without any fractals applied to it this just looks like a smooth box.
The walls of the canyon are being displaced with a redirectshader on a single axis.
The fun thing of this technique is that you can align another heigthfield next to it, so in parallel.
Using the same redirectshader will automatically create a twisting canyon
Further voronoi-functions, strata and powerfractals are applied for displacements and coloring.
