Deesis Hagia Sofia

Although the exact date of the creation of the mosaic is unknown. There are no surviving Byzantine writings that mention it and Byzantine artists usuially did not sign their works. Based on style it is possible to attribute the mosaic to a specific period of Byzantine art from late 12th to mid 13th centuries. It is believed that the mosaic either dates from 1185 - 1204 (in 1204 the city fell to Crusading armies ending all artsistic patronage in the city) - or just after 1261 when the Byzantines regained their capital from the Latin invaders.

http://mosaicartsource.wordpress.com/2007/01/19/john-the-baptist-mosaic/
http://www.pallasweb.com/deesis/history.html