Complex Cliffs and brushes that look good

I visited the tutorials on complex cliffs and stuff, and i dont really know what the term is called, but I need a tutorial or something on how they made the brushes in D17_coast (i think thats what its called) such as the cave at the beginning. I clicked on the brushes and it says they are a 6 sided solid brush. And when you look at it in the wireframe XYZ camera views it shows it as a cube, or a rhombus (whatever shape it was). When I click on it in the 3d camera view it shows many many more faces than 6, and the underside of the brush doesn't even have a face. If anyone has a clue as to what i'm talking about or would like to help me that would be wonderful.

Which bit of http://www.snarkpit.com/editing.php?page=tutorials&game=HL2&id=124 don't you understand? What you're talking about is a displacement surface, and there's a few other tutorials here about them. Start with this one:

http://www.snarkpit.com/editing.php?page=tutorials&game=HL2&id=112

Cool thanks! also, i remember watching an E3 video of hl2 before it came out, and it had a section where the ground was morphing. is that what displacement surfaces are for?

No, that's not even possible (Or at least not allowed, probably for performance and stability reasons) anyway.

Displacementmapping is what you do to create realistic clifffaces, round pipes (If you couldn't find a suiting model) and round corners along with anything else you want a more complex shape but don't have a model at hand.

You could create world brushes and tie them to a func_door
entity. That would give the illusion of morphing, anyway.

so what does "Env_TerrainMorph" do?

it morphs the terrain of course, but unfortunately it doesn't create clipping hulls in the morphed terrain. You could tell it to create a mountain in front of you, but then you could walk right thru the mountain as if it weren't even there. As Joe-Bob said you could use doors to achieve a similar effect.