I have compiled what I believe are the most interesting entries into my own custom COD zombies iceberg.
Levels:
Intro 0:00
The Sky 0:23
The Surface 1:48
Shallow Waters 5:04
The Depths 7:47
Twilight Zone 12:08
Midnight Zone 17:01
The Trenches 20:10
The Abyss 22:54
Outro: 26:43
Read about Unit 731: https://en.wikipedia.org/wiki/Unit_731
Enjoy :)