Roger Gilbertson's Ted Talk about that special civilization which built or helped build those special structures we can't duplicate today
You can skim the first few minutes I think to get to the meat of Gilbertson's inquiry; he's not advocating ancient astronauts or other hypotheses we've been subjected to. He's merely ques- tioning, with some evidence, that there does seem to have been a more advanced human species that was decimated by some cata- clysmic event. His final commentary is rational and interesting -- even edifying.
RR


