What is the deal with ""Argatha"?

[Mr.Zambezi]

I recently visited a buddhist retreat called “Shambhala.” Afterwords, I noticed the term in various places. There is a Shambhala Press and of course, the unforgetable 3 Dog Night song “Road to Shambala.” This led to a website that discussed Argatha.

From a web site I found this discussion of Argatha, the sister city underground:

The first public scientific evidence of Agartha’s existence occurred in 1947 when Admiral Richard E. Byrd of the United States Navy flew to the North Pole. Instead of going over the pole -he actually entered the inner earth. In his diary, he tells of entering the hollow interior of the earth, along with others and traveling 17 miles over mountains, lakes, rivers, green vegetation, and animal life. He tells of seeing tremendous animals --resembling the mammoths of antiquity moving --through the brush. He eventually found cities and a thriving civilization. The external temperature was 74 degress F.

WTF? Is this some kind of Art Bell fantasy? Anyone know where this came about?