Is Castle Volkihar supposed to be visible from long distance? Because it sure isn't showing up for me. Mods can be ruled out, I've already tested for them.

http://i.imgur.com/OjJOw.png

http://i.imgur.com/vf8id.jpg

Is this on PC? If so, I may suggest trodding over to the UDGP thread on the Skyrim mods forum. For one person, the bug appears to have been caused by another mod's LOD files were overwriting the Castle.

That's what it turned out to be. Updating the mod in question with the conflicting texture resolved the problem. But it also brings to light another problem, which I think is worth a new thread.