Humans love secrets, and are deeply intrigued by unexplained phenomena. When those secrets persist for hundreds or even thousands of years, the stories can be universally fascinating. Like the Antikythera mechanism, an unsettlingly modern machine found in the undersea wreckage of an ancient ship. Or the buried army of thousands of life-size Chinese warriors carved in stone. From lost cities to the Holy Grail to the identity of Jack the Ripper to the secret burial place of Attila the Hun, we leverage modern science and understanding to shed light on history's most enduring mysteries.