There's supposedly some cave system in the Grand Canyon that is protected as off limits to the public by the government that clearly shows that some advanced race lived there millenia ago.
Thats protected Indian Reservation land. The Navajo will guide people to it, but no camera's or other recording devices are allowed. From what I have been told by other archaeologists who have been there is that its pretty interesting Native American stuff that dates to about 1000AD.
There's also the space alien stuff that keeps people paying the really high priced guide service, which is why you cant take pictures.
