: These structures could have inner and outer walls so they could be half in
: and half out of the ground. If they are completely buried then the outer
: walls could be removed by the engine to save resources. Openings are just
: door frames that you place in the solid walls and they become entrances.
: You can place ledges, ramps, roads and tunnels up to them.

: I'd also have a selection of cave interiors to place in cliffs and under
: ground.

: Maybe we need a canyon digger and we could remake AotCR.

The interior space of a building would somehow nullify the floor.