Agartha (Agharta) is the name given to the imaginary world believed by some to exist inside the Earth and now incorporated into a number of the Hollow Earth ‘theories’^(a). In fact, Agartha or as he called it ‘Asgartha’ was invented by Louis Jacolliot (1837-1890).

One site offers video clips to support the Hollow Earth idea^(e), a concept first proposed by Edmond Halley in 1692⁽ⁱ⁾. In fact, the leading Electric Universe proponent, Wallace Thornhill, recently expressed sympathy for both a hollow Earth as well as a Hollow Moon. This was at a recent EU conference and can be viewed at the 40-minute mark of a YouTube video.^(h)

In 2001, a father and son team, Kevin & Matthew Taylor, combined the hollow earth theory with the idea of an expanding earth in their book, The Land of No Horizon^[823], as well as a YouTube clip^(f). 

The background to the 20th-century upsurge in interest in the idea of a Hollow Earth is worth a read^(c).

>Brinsley Le Poer Trench was a member of both British and Dutch nobility with the titles of 8th Earl of Clancarty and 7th Marquess of Heusden and had a seat in the British House of Lords. He held a number of extreme opinions regarding extraterrestrial visitors, UFOs and the Hollow Earth Theory and wrote a number of books in support of them. In 1974 he published Secret of the Ages ^[778]+, which was later republished as Finding Lost Atlantis Inside the Hollow Earth and is still available.<

A number of 20th-century writers have suggested that subterranean Agartha has a civilisation related to that of Atlantis. We should not be surprised by the existence of Hollow Earth theories, after all, the Flat Earth Society^(b) is alive and well and functional in California(see Eric Dubay). An international Flat Earth conference in November 2017 was reportedly sold out^(g).

It seems that no matter how daft the idea, followers are always available.

One website^(d) describes our hollow earth as the home of the lost tribes of Israel which they defend with flying saucers.

^[778]+ Secret Of The Ages (archive.org) *

^(a) The Inner Earth & Realm of Aghartha (archive.org) *

^(b) https://en.wikipedia.org/wiki/Flat_Earth_Society

^(c) The hollow Earth theory (archive.org)

^(d) https://www.ourhollowearth.com/

^(e) https://web.archive.org/web/20150919124636/https://thetruthbehindthescenes.wordpress.com/the-hollow-earth-theory/

^(f) https://www.youtube.com/watch?v=aAkcugev2Yw

^(g) https://boingboing.net/2017/11/12/dupes-gather-at-sold-out-flat.html

^(h) https://www.youtube.com/watch?v=Gouqy4OghyY

⁽ⁱ⁾ https://dioi.org/kn/halleyhollow.htm