Book excerpt: James Cross Giblin, this year's winner of the Sibert Medal, has written a stunning exploration of one of history's most mysterious structures. The Great Sphinx is one of the largest sculptures in the world. Six stories high and a city block wide, it has stood guard over the pyramids of Egypt's Giza Plateau for 4,500 years. Who built the Sphinx and why? And how did primitive sculptors manage to carve such a towering monument? In search of answers, James Cross Giblin takes readers back to a time before written history and traces the trail of clues left behind by the ancient Egyptians. As he explores various theories, Giblin seamlessly incorporates fascinating information on the pyramids, the Rosetta Stone, Atlantis, and more.