I want a colony on Mars that builds BOTH ways, up and down. Domes or structures that go up normally, but a large portion of the colony would be levels underground.
I think this would allow you to take advantage of keeping things pressurized (I think - with help of course, not just plain caves) and keep people safe from dangers of the surface. Possibly help with temperature regulation?
Colonists could travel to the surface to act in various capacities, but mainly live in the underground section.
So would it be viable to have say 20-40 levels? If it were 20 feet per level (to account for space between, infrastructure, etc) at 40 levels that's not even 1KM down. What would be the pros/cons of this approach?