This is a common idea - in a way it is as a shorcut to piling dirt on top of a structure that you make. Critics often bring up that exerting a huge force on the

This is a common idea - in a way it is as a shorcut to piling dirt on top of a structure that you make. Critics often bring up that exerting a huge force on the inside of lava tunnels might destabilize them in bad ways, and that sealing rough surfaces might be harder than just building a pressure vessel of your own.