Thanks for your reply, I just got a reply about this on usenet as well, where I had asked about it first. The poster said that all the dungeon levels are sort of jigsawed together onto one (or more) BIG maps, and that what I see is probably part of another dungeon that I will get to later. That makes sense I suppose, I have also seen red dots on the minimap just outside of areas I can get to, and assumed that was also a secret area. But it could just be other dungeon areas I guess.
Thanks for the welcome. I really dig this game so far, and plan to play it quite a bit in the near future, so I may come back with more questions.
Thanks again for your help.
EDIT: thanks to BOTH of you, I sent that reply before I saw both replies.