The Nimrud Lens
750–710 BCE
A 2,700-year-old piece of polished rock crystal discovered in the ruins of the Assyrian palace at Nimrud, Iraq. It has a focal length of approximately 11 cm, making it a functional magnifying lens. If the Assyrians possessed optical technology, it could explain how ancient craftsmen produced the extraordinarily fine detail found on Assyrian cylinder seals — detail that appears to require magnification to create.