Machu Picchu
Eric Von Daniken, in his series of books beginning with Chariots of the
Gods theorized that the Andean stoneworks were built by Alien/Gods who visited
the earth long ago, bringing civilization to primative man. The scientific community
simply snickered.
Whatever one thinks of his theories, he brought to the public an awareness
of the many ancient monuments on earth that seem to defy rational explanation.