On the first floor is a part that was originally only accessible to the imperial family. It contains the so-called deesis-mosaic, it represents Christ enthroned with on one side the Virgin Mary, on the other John the Baptist. It is from the beginning of the 14th century, and is an example of (Enc.Britt.) a “phenomenon called the Palaeologian Renaissance (from the dynasty of the Palaeologians, 1261–1453) led to a renewal of Byzantine mosaic art. The stylistic innovations that made themselves felt both in painting and mosaics of the late 13th and beginning 14th century bear witness to one of the most startling changes that ever took place within the framework of Byzantine culture. Bred by a vital humanism, which penetrated westward and laid the foundations for the Italian Renaissance, painting showed a predilection for perspective and three-dimensionalism. A peculiar vivacity invaded religious art, together with a sense of pathos and of the tragic. The results, as expressed in mosaics, were extraordinary.
To respond to the new trend, mosaicists recast their technique. The tessera size generally became smaller than it had been in earlier epochs; and contours lost their rigidity, became thinner, and were occasionally abolished. Colour was reintroduced in a manner that gives the Palaeologian works a striking likeness to the mosaics of the Early Christian period, which, one must suppose, in many cases served the artists as models.”