Absolutely. There are legends of a deeper inner Earth in South America.

But the basis behind some of it is found in the Tayos cave system linked, it runs according to their beliefs across South America. Or potentially for 100s of km. At least on some of the current exploration potentially linking Ecuador and Peru. On reading the first linked notes of origin, any artifacts came from a pyramid underground which is seemingly suggested on some of the metal tablets. It supposedly hasn't been discovered yet. But the items are of unknown origin as in the writing on much of them remains undeciphered. There is also the muddled mention of giants linking into its lore.

How and why it hasn't hit the mainstream, despite celebrity attention presidents, astronauts. Come on. Why is it still fringe, conspiracy. It undermines the narrative.