Erich van Daniken wrote a lot if interesting stuff in the 70's, based on his theory that ancient religions were based on visits from extraterrestrials. Most of his stuff was just CRAZY, but a good read nonetheless. I do recall reading about him exploring some mysterious tunnels that were discovered running throughout South America.
I don't know too much about lost cities, but what about other historical conspiracy thoeries? There is a lot of interesting stuff out there about grail legend and the knights templar, even if barely half of it is true.
I want to read a good book about Pompeii.... Dunno if there is even such a thing out there. Maybe I'll write one!
Yeah let me know, I loveeee pompeii