Possible Main Themes for The Huge Ruined Pile

Dwellers Beneath The Pile

• Underground Forgotten City: populated by nuclear/zombie fallout survivors, drow, dwarves, Snake Men, and so on...
• Collapsed Underground Civilization: once populated by [see above].
• Sorcerer's Domain: name level Magic-users should be really building dungeons instead of strongholds/towers.
• Fallen Starcruiser: the original crew may or may not be still onboard, but The Mad Computer is of course still working. Perhaps he has killed all the people onboard while they were cryogenically hibernating.
• The Reversed World: the entire world is underground, with no passages to the surface.
• Buried Temple: you know, something between Dante Alighieri's Inferno and Rappan Athuk.
• The Black Ziggurat: A truly expanded and re-designed "Lost City" from module B4.
• Other? Feel free to submit further ideas!

Right now I quite favor the Sorcerer's Domain. The idea of the identification between the Dungeon Master and the truly Mad Sorcerer who built the megadungeon in order to contain his very unspeakable secrets sounds just pretty cool to me.