If you put the camera inside a cube, you'll find the cube is already hollow. If you want to render reflective surfaces in interior scenes, create four walls, a floor and a ceiling, so there is something to reflect. As far as turning off the atmosphere, be sure to set haze and fog to zero, unless you want them inside. Welcome to Renderosity!

This is not my "second childhood". I'm not finished with the first one yet.

Time flies like an arrow; fruit flies like a banana.

"I'd like to die peacefully in my sleep like my grandfather....not screaming in terror like the passengers on his bus." - Jack Handy