Dungeons are underground caverns that house one of the stones of virtue.  It will also be connected by one or more of the 3 altars located on the 8th floor of the dungeons.  I will also list other dungeons that are found in the game.  If you've noticed, the dungeon's names are the opposite of the virtue.  When you reach one of the stone's room, you will see a someone guarding the stone.  They will ask you a question, and you must answer it correctly in order to get it.  If answered wrong, you will be warped from the dungeon.  The answers are 'yes', regardless of how the questions sound.  When in the Altar rooms, stand on the center marking, and use Search.  It will then ask you to put in the correct stones for that alter to get one of the 3-Parts Key.

Also, the dungeon's maps are viewed in a 8 x 8 square area.  When looking at them, it may seem a little odd that some of the paths don't really make since if you look at them; mostly because the maps have a wrap-around effect (meaning, if you go all the way in one direction, you will come back the other side).  Also, everytime you look at the map, it moves when you move to keep you centered in the map screen.  Some of them are just plain weird (such as coming down a ladder, walking 8 steps north, south, east or west and coming back to that same ladder.. not actually possible).  Anyway, I've altered some of the maps to give them defined edges, so they look like an actual map; whilst others I couldn't do that so I left them as is because they're being stoopid.
Virtuous Dungeons
Dungeon of Honesty - Deceit
Dungeon of Compassion - Despise
Dungeon of Valor - Destard Dungeon of Justice - Wrong
Dungeon of Sacrifice - Covetous
Dungeon of Honor - Shame
Dungeon of Spirituality - Hythloth
Other Dungeons
Serpent's Spine Mts.The Great Stygian Abyss