Mention of the Pyramids reminds me of an interesting little book I read a couple years ago. It was written by a French chemist who specialized in inorganic compounds (geopolymers) of which Portland cement is only one. He became convinced that the Pyramids were built not of stone blocks laboriously shaped and hauled into place, but cast in place with a mixture of minerals, using the same casting forms over and over. This makes sense to me. He gave a lot of reasons that I accept. But since he is not a card carrying archaeologist, nobody will pay any attention to him.
His name was Davidovitz, and I used to be able to find his site on the Internet using a combination of Pyramids and his name. It may not be there any longer. I have noticed that Yahoo dumps some things over ten years old.
http://www.mm2000.nu/sphinxh.html 
