Terrain Toolkit

Throughout the duration of the video one of the links talked about an expansion pack called 'Terrain Toolkit' this package is used to generate the fundamental structure of your terrain. It also comes with a selection of pre-set landscape types, which you can then adjust using the tools already provided within unity. The terrain toolkit also provides a texturing option. This is useful as it detects the different depths of your terrain and matches the textures to those depths. For example, our level is a rocky mountain wasteland so there was always going to be two contrasting textures from the start. One being the textures of the ground and the other the mountains surrounding the enclosed area. By just adjusting the texture contrast I can match it up perfectly that the ground textures covers only the area of the ground and the mountain texture to the mountains in my level however, the transition between the two at the mountains summit is seamless providing more believability.
I personally found this extremely helpful because it provided my terrain with depths that I myself might not have been able to convey through making the terrain from scratch and also produced high accuracy in terms of the texturing.

To download Unity and the Terrain Toolkit:
http://unity3d.com