I have this same problem. I have created my tomb exterior like this:
http://www.creationkit.com/Bethesda_Tutorial_World_Hookup
I actually putted my tomb in exact same place that it is in the tutorial. When I first time arrive near the tomb, only the door is visible and everything else is invisible. And when I go inside the tomb and come out, everything shows perfectly. So where is the problem?? I need help with this problem or I can't never get this tomb finished
