I was at Itaipu Dam in 1973 or 4 something during my visit to Iguacu and it was an incredible engineering feat at the time. One of the most amzing things I had ever seen. I must say that the water conservation at Petra a few thousand years earlier was an accomplishment that BLEW MY MIND. I never expected that sort of brilliant SIMPLE engineering in the desert!
PS--the Petra reference was regarding ancient history--not lke I was THERE...