For this one I used a World Machine 2 terrain as a base.
In TG2 I only added mild redirect shader displacements, 2 strata shaders and fake stones + about a half a dozen of surface layers.
Rendered with detail 0.8, AA8 with Catmull-Rom, GI 3/6/4, 64 atmo samples and of course soft shadows.
For postwork I went for something almost surreal and more artsy.
Cheers,
Martin