Originally posted by Delle(DK):

instead of digging tunnels or caves, the player can finding a cave in the game and kill what is inside and use it as a base ;-)
But tunneling would be nice below a base. Typical i dig a trench/hole and then setup wood beams and build a wood floor above and a building on top of that and then i have a basement or tunnel that way. ( or build a tunnel via stones )