I speak from a skeptical but interested position: the theory is Tartaria. According to the belief, there have been segments of a global, technologically advanced empire that held major chunks of the planet until major mud floods wiped them out.

Its an interesting theory, and I do believe there has been some major toying with our history (Phantom Time theory is another good one), but I also do think that major aspects of the theories ARE a bit far fetched. Interesting, great material that I aim to use as inspiration for some of my own fiction but still, far fetched.