Terrain on the ceiling/cinemachine rotation

I'm making a game where the terrain is above and the sky is below, I've looked at unity's video on the built in terrain editor and uts what i need except i can't rotate it to be on the ceiling. I also can't find a way to make the sky come from the botton and the directional light just turns to night when its facing up.

I could just reverse all my code to up instead of down and set the gravity in the opposite direction, but i also don't know how to set up cinemachine to rotate the other way.

It's a lot of work either way but i decided that it would be a lot easier to just find out how to make the terrain on the ceiling or at least how to rotate the framing transposer for cinemachine.

Does anyonr know how to either rotate the framing transposer or an efficient way to work on terrain on the ceiling/reverse skybox? I thought of using blender to just make the terraim but I'm not sure if its going to be an ideal way of doing it performance/resource wise.