Raiseland is a procedural terrain generator that can produce realistic & non-realistic terrains in minutes. You can use them on your favorite game engines and 3D editors: Unreal Engine, Unity, CryEngine, Leadwerks, Blender and many more.
It is surrently on sale but wont be available for long!!..
http://store.steampowered.com/app/388820/Raiseland/