Time stamps:
1:19 - Sky Texture
1:46 - Toggle on Sky in editor
2:00 - Worldspawn options
2:36 - Light_environment
5:09 - Block tool revisited
5:37 - Spike shape
7:37 - Vertex Tool
9:00 - Rock shape
10:23 - Cylinder shape
11:15 - Hollow out block option
12:52 - Water
13:31 - Func_water
14:31 - Cliff making
15:14 - Clipping Tool
17:26 - Vertex on Cliff
18:33 - Texturing Cliffs
18:56 - Duplicating Cliffs and adjusting them
19:25 - Adding sky behind cliffs