The first element of Nazi occult beliefs was in the mythic land of Hyperborea-Thule. Just as Plato had cited the Egyptian legend of the sunken island of Atlantis, Herodotus mentioned the Egyptian legend of the continent of Hyperborea in the far north. When ice destroyed this ancient land, its people migrated south. Writing in 1679, the Swedish author Olaf Rudbeck identified the Atlanteans with the Hyperboreans and located the latter at the North Pole. According to several accounts, Hyperborea split into the islands of Thule and Ultima Thule, which some people identified with Iceland and Greenland.
The second ingredient was the idea of a hollow earth. At the end of the seventeenth century, the British astronomer Sir Edmund Halley first suggested that the earth was hollow, consisting of four concentric spheres. The hollow earth theory fired many people’s imaginations, especially with the publication in 1864 of French novelist Jules Verne’s Voyage to the Center of the Earth.
https://studybuddhism.com/en/advanced-studies/history-culture/shambhala/the-nazi-connection-with-shambhala-and-tibet 