Ok is time to "break" the illusion, and show how to do a Giant character quite easily.
The Source Engine uses an optical illusion to save resources, instead of drawing a giant skybox, the engine draws a small one, and then it "reflexes" the skybox on the map, so you can put anything inside the box, and it make it looks giant, the problem?, is just a reflection, so the character can't interact with anything.
I don't know if i will make more tutorials in the future, but here is.