I saved the link to The 10 Most Puzzling Ancient Artifacts last week. I forgot about it over the weekend, but checked it out again today. If it's at all true, it's cool as hell. In general, the artifacts bring into question the chronology of human history as we know it. My favorite one is the Dropa Stones. (Note: Everything I say from here on out is from the article. I have NO idea if it's true). The Dropa Stones are 10,000 to 12,000 years old and were found in the Himalayas in China. The stones are circles that are 9 inches in diameter and appear to be ancient phonograph records. "The spiral groove, it turns out, is actually composed of tiny hieroglyphics that tell the incredible story of spaceships from some distant world that crash-landed in the mountains."
Check out these pictures from the Library of Congress - America in Color, 1939-1943.