The Mosaics of Hagia Sophia (6th–14th century)

Before it is a collection of mosaics, Hagia Sophia is a church — more precisely, the theatre of the imperial liturgy. Its images can only be understood by placing them back in the sound and ritual space for which they were designed: the chant of the Divine Liturgy, the processions of the emperor and the patriarch, the smoke of incense rising toward a dome contemporaries compared to heaven.

"The Great Church" of Justinian (537)

Today's Hagia Sophia is the third church raised on the site. The first two had burned down, the last during the Nika sedition of 532. Emperor Justinian I at once decided to rebuild on an unheard-of scale and entrusted the work to two scholars, more geometers than architects — Anthemius of Tralles and Isidore of Miletus.^[6] In only five years (532-537), they raised a dome nearly 31 metres across, set on pendentives above a vast vessel bathed in light. Tradition holds that on the day of the dedication, 27 December 537, Justinian cried out before his work: "Solomon, I have surpassed thee!" — a phrase found only in later accounts, legendary rather than direct testimony.^[7]

The historian Procopius of Caesarea, a contemporary, left the most famous description of the building: the dome, he writes, seems "not to rest upon solid masonry, but to cover the space as though suspended from heaven by a golden chain".^[8] This impression of luminous weightlessness is the very theological intention of Hagia Sophia: to give a foretaste of Heaven.

The architecture of light

The genius of Hagia Sophia lies in its light. A crown of forty windows pierces the base of the dome; further openings cut through the tympana and the small apses. As sunlight streams through these openings, it strikes the gilded surfaces of the vaults and spreads into a floating brightness that seems to dissolve the mass of the stone.

This is where mosaic enters the scene. The gold-glass tesserae (cubes of glass in which a leaf of gold is sandwiched between two translucent layers) are not laid flat: each is set at a slight angle of its own, so that light rebounds in a multitude of shifting reflections. A golden vault of Hagia Sophia is never still: it shimmers as the faithful walk by. Byzantine mosaic is, by nature, an art of light as much as of colour — which sets it apart from fresco and makes it incomparably more costly.

A decoration almost without images at first

The original mosaic decoration, Justinian's, was essentially non-figurative: immense fields of gold, plant borders, medallions, and above all radiant crosses. Neither Christ nor the saints were depicted in the 6th-century Great Church.

This restraint was not iconoclasm before its time: figured Christian art existed everywhere else, notably in the contemporary mosaics of Ravenna, where Justinian and Theodora had themselves portrayed (see the mosaics of Ravenna). But Hagia Sophia's programme gave pride of place first to the glorious cross and the light of gold as symbols of the divine presence. The great figures would come later — and their arrival would itself be a genuine theological manifesto.

To grasp the significance of Hagia Sophia's figured mosaics, one must recall the question that tore the Christian East apart for over a century: do we have the right to depict God? The full story of this controversy is told elsewhere; its essence is kept here, because the Virgin of the apse was born as an answer to that question.

From the Incarnation to the icon

The decisive argument of the defenders of images is not aesthetic but Christological. God, in himself, is invisible: "No one has ever seen God" (Jn 1:18). But "the Word became flesh" (Jn 1:14), and Christ is "the image of the invisible God" (Col 1:15). Since the Incarnation, the Invisible has made himself visible: to refuse to paint Christ is, at bottom, to refuse that he took true flesh.^[9]

Saint John Damascene, the great doctor of the image in the 8th century, put it in a single stroke:

"In former times, God, who is without form or body, could never be depicted. But now when God is seen in the flesh conversing with men, I make an image of the God whom I see." — Saint John Damascene, Discourse against those who reject the holy images, I^[10]

The icon is therefore no concession to popular weakness: it is a corollary of the dogma of the Incarnation. That is why the council would say that the honour paid to the image passes to the prototype — we do not venerate wood or tesserae, but the one they show forth. For this whole foundation, see the theology of the icon and the difference between icon, idol and sacred image.

The iconoclast controversy and the Triumph of Orthodoxy (843)

This doctrine was won through hard struggle. Two waves of imperial iconoclasm — from 726 to 787, then from 815 to 843 — forbade and destroyed holy images on the pretext of fighting idolatry. The Second Council of Nicaea (787), the seventh ecumenical council, solemnly restored the relative veneration of images.^[11] But a second restoration, in 843, was needed to close the crisis for good: this is the "Triumph of Orthodoxy", still commemorated on the first Sunday of Lent in the Eastern Churches.^[12]

Hagia Sophia's figured mosaics are the daughters of this triumph. The Great Church, left almost bare of images for three centuries, became the place where the victory of the icon was proclaimed in gold. For the details of the controversy, see the iconoclast controversy.

The first great figured image of the post-iconoclast Hagia Sophia is the Virgin and Child of the apse, in the semi-dome above the altar. The Mother of God, Theotókos, sits enthroned without a backrest, the Child Jesus on her knees, against an immense gold ground. It was inaugurated on 29 March 867, under Emperors Michael III and Basil I.^[13]

The homily of Photius, "the beginning of orthodoxy"

For the dedication, Patriarch Photius delivered from the ambo a homily that has remained famous — his Homily 17 — one of the finest commentaries ever written on a work of Christian art. In it he describes the Virgin as though she were alive:

"To such an extent have the lips been made flesh by the colours, that they appear merely to be pressed together and stilled as in the mysteries — and yet their silence is not at all inert; and the beauty of her form is not a mere copy, but the true archetype itself." — Photius, Homily 17, 29 March 867^[14]

Photius reads the image as the visible seal of the return to the true faith: to depict Christ and his Mother anew is to confess the Incarnation. The restoration of images is, he says, the beginning of orthodoxy recovered.^[15] The apse also bore an inscription — now fragmentary — summing up the event: "The images which the impostors had overturned here, pious sovereigns have set up again."^[16]

A theology in gold

The choice of the apse is no accident. It is the holiest point of the church, above the altar where the Eucharist is celebrated. To place the Theotókos bearing the incarnate Word there is to say visually what the liturgy accomplishes below: God gives himself in the flesh. The Virgin is not there for herself; she is the living throne presenting Christ to the world, as the altar presents his Body.

The gold ground is no mere decoration: it figures the uncreated light, the space of God, outside time and shadow. Byzantine figures cast no shadow, because they already belong to the transfigured world.

The archangels of the arch

On either side of the apse, on the so-called bema arch, stood two full-length archangels, guardians of the sanctuary. The southern one, Gabriel, robed as a court dignitary and holding sceptre and orb, is remarkably well preserved; his counterpart, the Archangel Michael, has almost entirely vanished. They frame the Virgin as the heavenly court surrounds the throne of God.^[17]

Several mosaics of Hagia Sophia stage the emperors. Far from mere prestige portraits, these are liturgical and theological images: they show earthly power bowing before divine power, at the very thresholds the emperor crossed during the great processions.

The Imperial Gate: Leo VI prostrate before Christ

Above the Imperial Gate, the central entrance reserved for the basileus passing from the narthex into the nave, a mosaic of the late 9th or early 10th century shows an emperor — generally identified as Leo VI the Wise (886-912) — prostrate (in proskynesis) before the enthroned Christ Pantocrator, who blesses and holds the open book. On either side, two medallions: the Virgin and the Archangel Gabriel.^[18]

The image is a political act of faith: at the precise moment he enters the church, the master of the world throws himself to the ground before the only true King. The open book Christ holds bears a word of peace; some read in it a discreet allusion to the penance of Leo VI, whose four successive marriages had scandalised the Church.^[19]

The south-west vestibule: Constantine and Justinian

Above the door of the south-west vestibule, through which one once entered the narthex, a mosaic of the late 10th century presents the enthroned Virgin and Child between two offering emperors: on her left, Constantine presents her with a model of the City (Constantinople); on her right, Justinian offers her a model of Hagia Sophia.^[20]

The message is crystal clear: the City and its church are placed in the hands of the Mother of God, protectress of Constantinople. That the image brings together, across five centuries, the founder of the City and the builder of the Great Church shows that Byzantium understood itself as an empire set under the guardianship of the Theotókos.

Zoe and Constantine IX: a reworked face

On the eastern wall of the south gallery, an 11th-century panel shows the Christ Pantocrator between Emperor Constantine IX Monomachos, offering a purse (the imperial donation to the church), and Empress Zoe, holding a scroll.^[21]

The most telling detail lies not in what is seen, but in what was altered: examination reveals that the emperor's head was remade, and with it probably the name inscription and the empress's face. Zoe, married three times and reigning in her own right, most likely had the previous husband's head replaced with that of Constantine IX. This "state retouching", engraved in gold, is a striking witness to the dynastic upheavals of Byzantium.^[22]

John II Comnenus, Irene and young Alexius

On the same wall, a little further on, a panel dated c. 1118-1134 (often assigned to 1122) repeats the composition: the Virgin and Child stands between Emperor John II Comnenus, offering the purse, and Empress Irene of Hungary (Piroska), holding the scroll. On the return face of the wall, their eldest son, young co-emperor Alexius, his face already marked by the illness that would carry him off.^[23]

Irene of Hungary — a foreign princess become empress, famed for her charitable foundations (she would be venerated as Saint Irene) — here embodies the piety of the Comnenian court. The handling, softer and more colourful than the earlier panels, already heralds the evolution of the Byzantine style toward the Deësis.

On the far side of the south gallery stands the image many hold to be the loveliest in all Byzantine mosaic: the Deësis (from the Greek déēsis, "prayer", "supplication"). Three colossal busts, nearly two and a half times life size: the Christ Pantocrator at the centre, the Virgin Mary on his right, Saint John the Baptist on his left, both leaning slightly toward him in a gesture of intercession.^[24]

The return of orthodoxy after the Latin occupation

The Deësis is very probably tied to one precise event: the reconquest of Constantinople by Michael VIII Palaiologos in 1261, after fifty-seven years of Latin occupation following the Fourth Crusade (1204). For half a century, Hagia Sophia had been a Latin cathedral. Its restoration to Orthodox worship called for a grand gesture: the Deësis would be that monument of thanksgiving, celebrating the return of the true faith to the Great Church.^[25]

A new naturalism: the "Palaiologan Renaissance"

What strikes the viewer in the Deësis is the humanity of the faces. Flesh is modelled by minute gradations of tesserae, from light to shade, with a softness earlier Byzantine art, more linear, had never attained. The face of Christ unites divine authority and compassion; the Virgin's, a melancholy of infinite tenderness. Historians speak of a "Palaiologan Renaissance": a renewal of naturalism and psychological depth, contemporary with the beginnings of Italian painting.^[26]

The meaning: intercession at the threshold of Judgment

The theme of the Deësis is Judgment: the Virgin and the Forerunner, the two greatest intercessors, pray to the Judge for humanity. Set in the gallery where the emperor and the court stood, the image reminded the powerful that, before Christ, they too would need the mercy obtained through the saints' prayer. It puts into pictures the communion of saints and their mediation with Christ.

Beyond the famous great panels, Hagia Sophia preserves other mosaic figures completing its programme.

In the niches of the north tympanum, beneath the high windows, survive full-length portraits of Church Fathers and patriarchs — among them Saint Ignatius of Antioch, Saint John Chrysostom and Saint Ignatius the Younger, Patriarch of Constantinople. They figure the continuity of the apostolic faith of which the Great Church claimed to be the guardian.^[27]

On the four pendentives carrying the dome watch great six-winged seraphim. Under the Ottomans their faces were covered with gilded medallions; one has been rediscovered and its face restored to view. These celestial powers, the closest to the throne of God in Isaiah's vision (Is 6:2-3), ring the dome as the court of heaven rings the Most High — while below, the chant of the liturgy endlessly took up their acclamation: "Holy, Holy, Holy, Lord Sabaoth."

The story of Hagia Sophia's mosaics does not end with their creation: it continues through a long effacement, then a resurrection before modern eyes.

1453: the church becomes a mosque, the images under plaster

On 29 May 1453, Constantinople fell to the Ottomans of Mehmed II. Hagia Sophia was at once converted into a mosque (Ayasofya). Since Islam forbids figured images in places of prayer, the mosaics were gradually covered with plaster and whitewash.^[28]

One often-forgotten fact deserves emphasis: it is partly thanks to this whitewash that the mosaics survived. Sheltered from air, light and hands, they crossed nearly four centuries of oblivion beneath a coat of plaster — instead of being hammered away like so many images elsewhere.

The Fossati brothers (1847-1849)

In the mid-19th century, Sultan Abdülmecid I entrusted a great restoration of the building to the Swiss-Italian architects Gaspare and Giuseppe Fossati. As they uncovered the vaults, they rediscovered the Byzantine mosaics, which they surveyed and drew with care — precious documentation, since some figures have since deteriorated again.^[29]

But the building remaining an active mosque, the Fossatis had to cover over most of the images after studying them, replacing them with painted decoration in the spirit of aniconic ornament. Their surveys and watercolours remain one of the great testimonies to the state of the mosaics in the 19th century.

Thomas Whittemore and the Byzantine Institute (from 1931)

The decisive turning point came in 1931, when the American archaeologist Thomas Whittemore, founder of the Byzantine Institute of America, obtained from the young Turkish government permission to methodically uncover and conserve the mosaics. Through the 1930s and beyond, his team removed the plaster, cleaned and stabilised the Deësis, the imperial panels, the Virgin of the apse and the other figures, and published scientific surveys that remain fundamental.^[30]

It is this patient labour that restored to the world, almost intact beneath their gold, works thought lost — and that enabled art historians to found the modern study of Byzantine mosaic.

Museum (1934), a mosque again (2020)

In 1934, as part of the secularisation willed by Mustafa Kemal Atatürk, Hagia Sophia was turned into a museum: the mosaics became visible to all, Christians and Muslims alike, and the monument became one of the most visited in the world.^[31]

In July 2020, a court decision and a presidential decree returned Hagia Sophia to Muslim worship. The figured mosaics were not destroyed, but they are now veiled (by curtains or removable devices) during prayer hours. The international debate this reconversion stirred shows how far these images reach beyond art history alone: they touch the Christian memory of the East and the universal standing of a masterpiece of humanity.

To Catholic eyes, the mosaics of Hagia Sophia are not merely splendid relics of a vanished empire. They are a preaching in light, faithful to the great intuition of Christian art: beauty is a path to God.

They say first that the Incarnation authorises the image: because the Word became flesh, his face can be painted without idolatry — that is the whole meaning of the Triumph of Orthodoxy these golds proclaim. They say next that art in the service of the liturgy is no luxury, but a way of drawing the faithful into the mystery: as Gregorian chant or polyphony for the ear, golden mosaic works for the eye, and both serve the same prayer. On this kinship of music and image in worship, see Bach and the Christian tradition.

They say lastly that beauty endures. Covered for centuries, veiled again today, these images have crossed empires, conquests and oblivions. The Virgin of the apse, whose lips Photius admired as "made flesh by the colours", still watches, in silence, over the Great Church — a stubborn witness that "the Word became flesh, and dwelt among us" (Jn 1:14).

• The theology of the icon — the doctrinal foundation of every Christian sacred image.
• The iconoclast controversy — the iconoclast crisis (726-843) of which Hagia Sophia's mosaics are the victorious outcome.
• The difference between icon, idol and sacred image — why venerating an image is not idolatry.
• Why does the Church use images? — the Christian pedagogy of the visible.
• Byzantine icons — the art of the painted icon, sister to mosaic.
• The mosaics of Ravenna — the great twin ensemble of Byzantine Italy.
• Bach and the Christian tradition — the same logic of liturgical art, in the order of sound.