Yes. You have to dig, possibly using explosives to blast through rock, and install more supports, ventilation, drainage, etc. In many places you need a lot of c

Yes. You have to dig, possibly using explosives to blast through rock, and install more supports, ventilation, drainage, etc. In many places you need a lot of concrete to support the structure too. You might think you're getting walls almost for free, but that doesn't happen often.