I think a sensible low-tech way to build a small-to-medium sized mars or moon structure is to dig a big hole, stack bricks or cut stone to form an igloo-like do

I think a sensible low-tech way to build a small-to-medium sized mars or moon structure is to dig a big hole, stack bricks or cut stone to form an igloo-like dome in the bottom of the hole, and then bury it in dirt with a staircase to get in and out. The inside can be sealed with an air-tight liner material and an airlock installed. The weight of the dirt counteracts the air pressure and protects against radiation and temperature variation. The bricks provide a rigid compressive structure to maintain the shape and hold up the dirt. The liner doesn't have to be particularly strong, just resistant to accidental tears. Theoretically, the brick dome could be omitted if you can exactly balance the weight of the dirt with internal air pressure, but that seems kind of risky (and every time the internal pressure fluctuates slightly, the dome gets a little smaller as the dirt settles). The hard parts of this plan are a) how do you get/make thousands of bricks? and b) how do you do all the excavation and assembly? It would be great if we could get robots to do the whole thing and have a habitat ready before humans arrive on the scene, but with current tech a lot of the work might have to be done manually by guys in space suits with construction equipment. I suppose once you have one habitat, it's a lot easier to build a second one next to it.