I'm not including Blackreach. I'm just wondering how many more dungeons (I don't need their names) I can expect of that size. I've spent over four hours just getting to Blackreach and enjoyed every minute of it.

I've been in some caves that took at least an hour to finish.

Labyrinthian is supposed to be pretty huge, though I haven't been there myself yet.

I've been just barely into Labyrinthian, and it shows not cleared for me. I should go back and clear it.
Also, Alftand was sizable, but needs I think a quest or 3 more into it.