The idea is to place 1 megadungeon in each of the 200 or so realms of Aerth.
So far...
* CASTLE REDSTAR, by @chris107 (Cymru, prehaps)
* RAPPAN ATHUK, by Frog Games / Necromancer Games (Tuscany, prehaps)
* NECROPOLIS, by Gary Gygax (Aegypt, of course)
I'd love to add some NETHACK and/or Appendix A dungeons to the list.
I think it's important to remind people not to feel limited by Fantasy Earth sources, such as the HR (Historical Reference) series.
Often, equipment etc. is limited, but the way that I imagine Aerth, in every realm, the full range of possibilities in the first 7
AD&D books exists, there.
So, for example, a 'Viking' (Norse) realm where there is no full plate and no rakshasas, according to the book(s).
Ignore the restrictions, and place full plate and rakshasas to your hearts' content.
Prespos
Ps.
Full plate and rakshasa in the same sentence... yikes... longpig vindaloo!