If he's trying out the demo, I don't think he has any scene. This terrain you see is a procedural terrain, and it was made by one of the best Vue artists. Procedural terrains are created using the function editor, by combining different fractal noise nodes and turbulences. I suspect the one above uses the "voronoi altitude" fractal noise. You can have smooth or had surfaces by changing the roughness parameter of the noise, and you can also apply the erosion effects of the terrain editor.