The Gemma Claudia is a very finely carved and detailed, five-layered, cameo in sardonyx, a type of onyx that has parallel layers of sard which depicts members of the Roman imperial Julio-Claudian dynasty. It is believed to have been created in around 49 AD and by the 17th century was owned by the Habsburg Holy Roman Emperors, later passing to the Kunsthistorisches Museum in Vienna. It is 12 cm high and set in an 18th-century gold circlet.