Some historical artefacts are destined forever to alter how the ancient world is perceived. The unearthing in today's Iraq (in 1879) of a clay cylinder-shaped decree from Cyrus the Great, founder of the Achaemenid dynasty of Persia, stands in the same tradition of game-changing discoveries from antiquity as Hammurabi's famous law code or the intact tomb of the boy-king Tutankhamun. For the Cyrus Cylinder contains in microcosm the whole history...