What a great scene you're working with, I especially like that sky. :) 1 - Try using a rock object for the cave itself, booleaned in the same way as the terrain object you used. The rock shape might be more what you're looking for and be less regular; it can also be edited to be even more "rocky" as desired. 2 - Experiment with the material settings. You can add Turbulence with just a click that will make an "instant" difference in the appearance. You can also add or remove functions and filters from the Bump or Color tabs. You could replace the stone material with an image map. Or you could Mix an image map and the stone material together for an entirely different look. What to do really depends on where you want to go with it.