This time I was in a strange stairwell. I started walking down it until I reached a weird cavern with a huge flame in the center of it. I wandered around a bit and found another exit, but a couple of old men were guarding it and wouldn't let me through. Eventually I got bored, walked back up the stairs and woke up.
The whole thing seemed very real, though. I think I'll see if the library has any books on lucid dreaming.