Appendices - Strolling Through Istanbul: The Classic Guide to the City - page 477

most typical are the two churches which form parts of the complex
building of St. Saviour Pantocrator (Zeyrek Camii).
All the Byzantine churches in Istanbul are built of brick, including
Haghia Sophia, and they were generally little adorned on the exterior,
depending for their efect on the warm brick colours of the walls
and the darker areas of windows which were usually plentiful and
large. Towards the end of the Empire in the thirteenth and fourteenth
centuries, exteriors were sometimes enlivened by polychrome
decoration in brick and stone, seen at its best and most elaborate
in the façade of the outer narthex of St. Theodore (Kilise Camii)
or in that of the palace of Constantine Porphyrogenitus (Tekfur
Saray). As if to compensate for the relative austerity of the outside,
the interior of the churches blazed with colour and life. The lower
parts of the walls up to the springing of the vaults were sheathed in
marble, while the vaults, domes and upper walls were covered in gold
mosaic. The most magniicent example of marble revetment is that
in Haghia Sophia where a dozen diferent kinds of rare and costly
marbles are used, the thin slabs being sawn in two and opened out so
as to form intricate designs. The Great Church was of course unique,
though there may have been a few others of Justinian's time almost
equally lavishly covered with marble. But even the humbler and
smaller churches of a later period had their revetment, largely of the
common but attractive greyish-white Proconnesian marble quarried
from the nearby Marmara Island. Most of the churches have now lost
this decoration, but an excellent example survives almost intact at St.
Saviour in Chora (Kariye Camii).
The mosaics of the earlier period seem to have consisted chiefly of a
gold ground round the edges of which, emphasizing the architectural
forms, were wide bands of floral decoration in naturalistic design
and colours; at appropriate places there would be a simple cross in
outline. Quantities of this simple but efective decoration survive from
Justinian's time in the dome and the aisle vaults of Haghia Sophia.
It appears that in Haghia Sophia at least there were originally no
pictorial mosaics. In the century following Justinian's death, however,
picture mosaics became the vogue and an elaborate iconography was
worked out which regulated what parts of the Holy Story should be