Sometimes in a Dungeon I have found that the exit to one of the levels is generated so close to one of the walls it cannot be seen unless you are standing right next to it. So if the dark areas of your map are uncovered and you do not actually pass right next to the exit you will never see it. It will also not show on your large map when you look at the whole level.
After finding this a couple of times I began dropping a flag that says "Room Done" in every room and every corridor to make sure I did not miss something.
That happen to me In a stone wall dungeon and it took me forever to find the next exit down. From then On I started flaging them. <img src="/ubbthreads/images/graemlins/beyond.gif" alt="" />
