Two mapping problems.

[FrivolousSam]

Just the default editor. The blocks I was placing were actually spaces, so you're able to create floating platforms just by placing spaces all around part of the terrain. Hollowing out the area, it functioned kind of like Unreal Engine 3 which I tried to get into using once for like a day then stopped.

[volum]

Nice idea, I tried it out and works nice. But I couldnt make my map as deep underground as your map. It just doesent go deeper than the 1 longest underground block size

Btw. If you use TMunlimiter you can place grass spawn point underground and it gives normal weapon and able to jump. You can also place poles underground. I just couldnt get deep enough so the poles head sticks out of roof hole. Is there any tricks how to make undergrounds more deeper?

[Extraneous]

Volum, to make underground deeper build hills on the surface with the terrain editor. Should help.