Lets start by saying that ever since I discovered this community I got really excited on the art called "geography".
I'm completely new with this, but more then eager to "master" it.

Now, in the near future I will launch a new continent on a RP-game server. And with that I would love to have a
good looking map with it. So I started searching for tutorials and started messing around with them. The only problem?
I can't find any underground-land-maps tutorials. It is sadly not like a small cave or anything. It is basically a continent
that is completely underground, so the dungeon map tutorials I found here
(or anything related with underground mapping anywhere, really) do not fit my requirement.

Are there any resources/tutorials I could get a hand on regarding this specific kind of map making?

Thanks a ton!