1. The room with the table and chair where you start. Going up from here gets you to the forest outside (8) but you can only go up if you are holding next to nothing and have very high health. You can only get the lightest treasures, like opal or tiara, outside this way.
2. The great library has a southern entrance. Maybe a quarter of the time it will get you to the east end of the great marble portal, which is one south on the map-grid. Usually you end up in the maze.
3. The room with a great pit. If you JUMP PIT, you'll end up on the northeast corner of floor 3. This is the first step of an important way to get outside.
4. The high narrow path with mist everywhere, two south of where you end up after jumping the great pit (3). If you JUMP from here (with no direct object--if you were really there this would be the scariest part of the game) you end up at the west end of a great pit filled with mist (5). This is the second step of an important way to get outside.
5. The west end of a great pit filled with mist. If you jump this pit, you end up at the room in the fourth floor maze with a pit (9). This is the third step of an important way to get outside. Note that this is the second-stingiest pit in the game, I highly discourage trying to jump it with anything in your possession except the lamp, and not trying to jump it at all if you're below 220 health or so.
6. There is a passage from the dark chamber to the twisting winding narrow passage and vice versa, but it rarely works--usually you end up in the maze. This is annoying because these rooms are difficult to get to otherwise, especially if there are any spells or blocked passages at all on that long, long route.
7. The stingiest pit in the game, bar none. It takes you outside if you make it, but if you are holding ANYTHING, and especially treasure, guaranteed you won't make it. Once you figure out the maze, you can get to the pit there in 30 seconds from here (barring blocked passages et al.), and if you need to get that sapphire outside I highly recommend going that route.
8. Outside, by a great forest. Where you need to take treasures in order to get 10 points for them. You can easily go down to the room where you started (1), but it is usually impossible to take any treasure back up again from below.
9. Jumping the pit here takes you outside (8). If you have full health, there is nothing in the game you cannot get outside by jumping this pit, not even the notoriously heavy rings. Just don't hold any more than one item (plus the lamp) at a time.
10. This room has green mist running down the east wall. I don't know what to do with the green mist, or if it does anything, but it is a good landmark if you get lost in the maze.
11. Going south from here takes you to a random place in the maze, either the part I have mapped, or the big maze, which I discuss next.
12. Almost forgot about these last two. This is the small dark tunnel. If you enter here with your lamp on, or LOOK after you light it in this room, yyou get a free treasure!
13. Since you can only get here by going through the small dark tunnel (12), you won't need to worry about this if you're smart. This is a narrow twisting stairway with no windows, and unless you have your lamp on, you will stumble and fall, and lose like 30 health points!