Well, my friend Alexei Panshin tipped me to this years ago -- that a Frenchman was convinced the pyramids were really made out of poured concrete. It made a lot of sense, since there are no partial blocks of limestone or tools lying around and the nearest quarry was hundreds of miles away. Now, it seems, an American scientis concurs.

ReadThe Surprising Truth Behind the Construction of the Great Pyramids

What's particularly interesting to me is the suggestion at the end of the article that this isn't about the past, it's about the future. For us moderns, concrete is one of the biggest energy sinks and contributors to carbon emissions. But the Egyptians did this stuff with human power and an intuitive sense of chemistry. What we could learn!