In 1973, Erich von Däniken, at the height of his fame following the success of his book, Chariots of the Gods, claimed that he had entered into a gigantic subterranean tunnel system in Ecuador, which he was told spanned the length of the continent—surely evidence that our ancestors were highly advanced, if not extraterrestrial. The structure was believed to house a library in which books were made out of metal—this in an area where today there is nothing but "primitive" Indian tribes with no written language. (1)
References:
1. The Quest for the Metal Library, by Phil Coppens: http://www.philipcoppens.com/metal_libr.html