There are a few of them:
- The tomb behind the gate on the left is the entrance to Lady Grey's Tomb, and opened during the quest Love Hurts. The tomb behind the gate on the right is the exit.
- The locked Castle door opens when you buy the castle for 1 million gold after the end of the main quest.
- The Demon Door unlocks when you have opened all the other doors.
- The door in the Fairfax Archaeological Dig Site opens when you have retrieved all of the Ancient Scrolls for Belle Rennock in the quest The Archaeologist.