This mosaic in the nave is the Archangel Gabriel wearing a divitision or undergarment, over which is thrown a chlamys or cloak of white silk; his great wings, reaching nearly to his feet, are of brightly-coloured feathers, chiefly green, blue and white. In his right hand he holds a staff, in his left a crystal globe, through which can be seen his thumb (Info from Strolling through Istanbul, 1989).