What makes a "good" dungeon?

I've been thinking about the question of what makes a good dungeon for a while now, so I think it's time to write down a brief summary of my ruminations.

1. A good map. The map is an important part of the dungeon. Thirty feet of passageway to room with orcs, followed by thirty feet of passageway to a room with kobolds, just doesn't cut it. Maps don't need to be Escher-like studies in insanity, but they do need to have enough caracter to make the players feel like they are going somewhere and not simply visiting the same room over and over again, or just following a straight path to the end of the dungeon.

2. A sense of scale. Dungeons in the old school sense were big places. Individual rooms might be small, but the overall impression should be that the dungeon is BIG.  The dungeon should cause players should feel that they are far from the lighted world above, especially as they moved deeper into the underworld. 

3. A sense of otherworldliness.  I 've always felt that the best dungeons are somehow separated from the day to day realities of the world above.  Sure, the dungeon may be situated beneath the ruins of a mad mage's castle, but it shouldn't be storerooms and privies.  The dungeon needs to be mysterious.  It should evoke wonder in the players and make them question its purpose.  That purpose may never be truly known, but it needs to engage the imaginations of the players.  Make your players wonder about things.  Keep their minds working.  The dungeon needs to almost be a character in itself and if handled well can in many ways be more interesting that either the monster or the loot found within it.

4. Room to grow.   A good dungeon needs room to grow.  Parties of adventurers will come and go and the dungeon may need to expand either downward of outward.  Make sure that there is room.

5. Care and feeding.  The best dungeons are never truly complete.  As adventurers come and go, things will change.  Old monsters will be slain, new monster will move in, inhabitants of the dungeon may form alliances or fight amongst themselves.  Dungeons are entities in a game and they need to be maintained.  A well cared for dungeon can provide countless adventurers for numerous parties.