Agartha

Agartha is a name given to a thriving world that exists underneath the earth's crust. The only known way into Agartha is through the Icelandic volcano, Snæfellsjökull.

League of Extraordinary Gentlemen: Humans
Upon entering the volcano, Snæfellsjökull, Gulliver's league discovers a thriving and prospering world that lies within the volcano. This world contains many animals thought to be extinct by humans, such as dinosaurs. Gulliver names this world, 'Agartha.'

Agartha is also home to a super race known as the Vril-ya, who have lived in Agartha for eons to escape from a massive flood on the earth's surface.

After escaping the Vril-ya, the league destroy the only known entrance to Agartha, trapping the Vril-ya inside and forever closing off the entry way to a whole other world.

League of Extraordinary Gentlemen: Spells
Upon hearing of a 'moon child,' Orlando believes that the child is an escaped Vril-ya and suggests to go back to Agartha and find out. He is then told by Thomas Carnaki that the child is human.