Detail of 4th-century porphyry sarcophagus of Saint Helen, mother of Constantine the Great (306-37). From the funeral hall of Santi Marcellino e Pietro in Rome. It is generally believed to have been originally made for Constantine himself. Its reliefs show Roman soldiers on horseback conquering prostrate, chained barbarians. Hall of the Greek Cross, Pio Clementine Museum, Vatican Museums (Musei Vaticani).