Spolia

Spolia (Latin, 'spoils') is the re-use of earlier building material or decorative sculpture on new monuments. The practice was common in late antiquity: Roman examples include the Arch of Janus, the earlier imperial reliefs reused on the Arch of Constantine, the colonnade of Old Saint Peter's Basilica; examples in Byzantine territories include the exterior sculpture on the Church of Panagia Gorgoepikoos in Athens); in the medieval West Roman tiles were reused in St Albans Cathedral, porphyry columns in the Palatine Chapel in Aachen, and the colonnade of the basilica of Santa Maria in Trastevere. Spolia in the medieval Islamic world include the columns in the hypostyle mosques of Kairouan and Cordoba.