Acknowledged as one of the great buildings of the world is The Church of the Holy Wisdom or also
known as Hagia Sophia, now a museum, it is a former Byzantine church and former Ottoman mosque in
Istanbul.

The Hagia Sophia has a classical basilica plan. The main ground plan of the building is a rectangle,
230 feet (70 m) in width and 246 feet (75 m) in length. The area is covered by a central dome with
a diameter of 102 feet (31 m), which is just slightly smaller than that of the Pantheon in Rome. All
interior surfaces are sheathed with polychrome marble, green and white with purple porphyry, and gold
mosaics. On the exterior, simple stuccoed walls reveal the clarity of massed vaults and domes.

The main dome is carried on pendentives: four concave triangular sections of masonry which solve the
problem of setting the circular base of a dome on a rectangular base. Each pendentive is decorated
with a seraphim. The weight of the dome passes through the pendentives to four massive piers at the
corners, and between them the dome seems to float upon four great arches.

At the western and eastern ends, the arched openings are extended by semi-domes. The flat wall on
each side of the interior (north and south) is called a tympanum, and each one has 12 large windows in
two rows, seven in the lower and five in the upper.

The Islamic calligraphic roundels suspended from the main dome since the 19th century remain in
place and make for a fascinating religious contrast with the uncovered Christian mosaics. The names
painted on the eight wooden medallions are: Allah and Muhammad (flanking the apse); the first four
Caliphs Abu Bakr, Umar, Uthman and Ali (at the four corners of the dome); and the two grandsons of
Mohammed, Hasan and Husayn (in the nave).

At ground level, most of the sights date from the Islamic period. A beautiful marble structure in the apse
is the mihrab, a niche found in all mosques that indicate the direction of Mecca. The large freestanding
stairway to the right of the mihrab is the minbar, or pulpit from which sermons were given. To the left of
the mihrab is the grand sultan’s loge, built by the Fossati brothers who restored the Hagia Sophia in the
1800s.

The best-known mosaic is called the Deësis Mosaic, and it is the first you come to as you enter the
South Gallery through the Marble Door. It depicts a triumphant and kingly Christ (known as “Christ
Pantrocrator”), flanked by the Virgin Mary and John the Baptist.

At the end of the South Gallery are two golden Byzantine mosaics. On the left is Christ with Emperor
Constantine IX Monomachus and Empress Zoe; on the right is the Virgin and Child with Emperor John II
Comnenus and Empress Irene.

The modern exit from the Hagia Sophia is through the Vestibule of the Warriors, so called because it
is where the emperor’s bodyguards waited while he worshipped. Up high and behind you as you walk
out is a splendid mosaic of the Virgin with Constantine and Justinian: Constantine the Great presents
to the Virgin a model of the city of Constantinople (Istanbul), which he founded, and Emperor Justinian
presents the church of the Hagia Sophia, which he rebuilt.