This sounds like a stupid question, when I say it out-loud, but I need a pointer.

I've been working on a map and the first level decends into the earth. I though I had that feeling but the more I look at it the more I really don't think I have any idea what I'm doing.

Basically I'm trying to get the effect that the ground level is at the base of a hill/mountain and the dungeon decends into the depts below.

Pointers appreciated.