You can use Bryce to import real-world DEM (from USGS) or create terrain meshes from within its editor. Then export the terrain mesh as an obj file for importing into Carrara. You'll have to play with the number of polys to export from Bryce to make it look detailed enough, depends on the camera angle. In Carrara use a glow channel color of dark gray mixed with height (front to back) on your terrain shader to "wash-out" the depth of color, this helps add dimmension.