I couldn't find Adrianne Avenicci, so I used the player.moveto command and ended up http://i.imgur.com/xG9V4ox.jpg. Sigurd was there as well, plus two dead NPCs, one of which had a named coffin.

1. What is this place? My guess would be some kind of "limbo" where dead NPCs are moved, but that doesn't explain why Adrianne and Sigurd are there.

2. If 1., how come alive NPCs end up there and when do they come back?

Weird.

It's called WIDeadBodyCleanupCell. It's where the game engine sends the bodies of named NPCs after they have been killed.

Thanks. Does that mean that Adrienne and Sigurd are dead even if they seem very much alive?

EDIT: Found this regarding the cell: "In regards to why some NPC's are walking around, I think the game also uses this cell to "store" poar widdle wost followers and NPC's, so on the frequent occasions when Lydia disappears (gone shopping for more bread rolls maybe?) She will sometimes end up there, until you stop moving long enough for the game to 'teleport' her back to you or her 'home' cell"

So I guess they are alive but for some reason have "glitched" there, only to get back to Whiterun after a while. At least I hope so - there are so few named NPCs in the towns and I wouldn't want Adrienne to disappear.

EDIT: I think I know why Adrienne was there. I used resurrect on her earlier, after she was killed by a vampire. After cell reset, I guess the game treated her as dead anyway as she perhaps was flagged as dead, so it moved her to the "graveyard" - although she was alive. I returned her and used the recycleactor command. Hopefully she will stay alive after a cell reset now. During my next playthrough I'll flag her and several other NPCs as essential from the start.