Ok I just did some more reading on Agartha, or Shamballa. This is from wiki:
...Cataclysms and wars taking place on the surface drove these people underground. These were said to include a lengthy Atlantean-Lemurian war and the use of thermonuclear weaponry that eventually sank and destroyed these two highly advanced civilizations. The Sahara, Gobi, the Australian Outback and the deserts of the southwestern U.S. are said to be but a few examples of the devastation that resulted. The sub-cities were created as refuges for the people and as safe havens for sacred records, teachings and technologies that were cherished by these ancient cultures...
...The inhabitants of Agartha are said to have scientific knowledge and expertise far beyond that of the people who live on the surface of the planet, lost technology from the days of Atlantis...
...There are no entrances to Agartha Alpha and Beta from any other part of the planet. The only entrances are in the Gobi desert itself and are secured by illusory technology that is beyond the comprehension of modern science...
In teresting the GOBI desert is mentioned, where the polar bear was unearthed, as well as Atlantis and Lemuria (mentioned elsewhere in this thread). Also, entrances to Shamballa or Hollow Earth are at the poles.