I voted 5-6

Though I only used three through any of my campaigns.

The Elokian Underground from TFH... Which I liked a lot.

A Atlantis never existed in any of my world (oddly considering how much I love it)... BUT I did use the aquatic Tyno Helig, city of Glacia's people from PES, which is the Welsh equivalent of Atlantis (which in a throwaway line from Glacia or Aqua as I called her, she said that Atlantis did not survive, it simply disappeared).

I did have a Cloud City that I never used. It was supposed to have something to do with the lost Aztec and deal with artificial winged people led by the embodiment of Quetzalcoatl... And deal with Marutukku and the visages of the Sumerian entity known as Marduk (which was likely pronounced Marutuk).

I would have used more... Certainly would now if I ever ran a campaign again... But alas I didn't previously.

They are fun... But can bog down the world. If they become a part of the world.

*shrug*

For a traditional comic campaign, these are mandatory IMHO. There are some things that just ARE required; Nazis, Aliens, Hyper-intelligent talking Apes, and Hidden civilizations. Some of these are of course, mashed together as needed.

I use:
The Blood: Alien Mutant Royalty: Created by Aaron Allston, Lifted from Champions, they substitute for the Eternals, and are much cooler.

Prime Ape City: My Hyper-Intelligent talking apes and their scientifically advanced city. Shamelessly stolen from DC Comics and Gorilla City. They have their own superhero team, the Prime Apes of course!

Neuschwabenland: Lifted from the Nazi name for their Antarctic expeditions, this is my Savage Land ripoff. Located deep underground in a caldera accessed via ice caves, it is populated by natives that are basically primitive grey style aliens, dinosaurs, and 4 human communities: Donnerville (Wild West Americans), Sanctuary (German steampunk style), The Empire (Pax Britannia run by Supervillains), and the Refuge (Small group of Muslim monks that barely interact with everyone else. Completely pacifist)

Atlantis: To my ongoing sadness, the group disbanded before they got here.

Shangri-La-la-la: Name was never set, but this is that mystical city of super martial artists you need for PCs and Villains.

In my game we have a new city/race of fish people ( who look like the sea monkeys from the ads in the back of comics) who live in a subterranean sea below Germany.

There is a race of blue humanoids that live beneath the USA.  It is believed they killed the lost colony of Roanoke as a sacrifice to their god.

A race of Dwarves live beneath Norway. And underneath them are some dark elves.


Some hidden enclaves of Illithids and Deep Ones live in the oceans.

Their are the Seven Occult Cities, only Shamballa has been discovered so far.

Atlantis/Mu/and Lemuria are long gone, about 40,000 years ago gone. BUT there are colonies on other planets and one has reached out to "help" us...

and there is evidence of a metahuman city hidden in Tycho Crater, on the Moon.