Roberto Nardi gives a lecture on the conservation of the mosaic of the Transfiguration at the Penn Museum (Philadelphia) on March 30, 2011. The Mosaic of Transfiguration is located in the apsis of the church of Saint Catherine Monastery, Sinai. The conservation intervention, directed by Prof. Nardi, was carried out between 2005 and 2010, and it rescued from collapsing an important masterpiece of early Byzantine art (6th century A.D.). The mosaic covers the church apsis and it shows an incredible chromatic richness because of the use of glass, gold and silver tesserae, as well as polychrome marbles. The intervention was planned by CCA on behalf of the Getty Conservation Institute (GCI) and realised thanks to private funding.