You reach the upper gallery of the Hagia Sophia by climbing a stone ramp worn smooth by a thousand years of feet. You turn a corner. And then you stop.

The face is perhaps six feet tall. It is made of glass — thousands of tiny tesserae in gold and brown and grey and green, each one set at a slightly different angle so the whole surface catches light the way water does. The eyes are not symmetrical: the left eye, Christ's right, is slightly larger, slightly more intense. This is intentional. It is the eye of divine judgment. The right eye, Christ's left, is softer. The eye of mercy.

He holds the Gospels in one hand and raises the other in blessing. His expression is the most complex thing made of glass in the history of the world: compassionate and severe, intimate and absolute, fully human and utterly beyond human. He looks at you the way someone looks at you when they know everything about you and have not yet decided what to do.

Glass tesserae (smalti) set in plaster, approximately 4–6mm square, in a grid that follows the curves of the face rather than a mechanical horizontal-vertical pattern. The gold background is gold leaf sandwiched between two layers of glass — a Byzantine technique that produces a depth and warmth impossible to achieve with surface gold. The flesh tones are built up in gradated layers from dark to light, following the Byzantine tradition of working from shadow outward. The scale is approximately 6 × 8 meters, viewed from below.

Pantocrator means "Ruler of All" — this is Christ as cosmic sovereign, not suffering servant. The closed Gospels in his left hand are bound with jeweled covers: the word of God, complete and sealed. The raised right hand makes the blessing gesture in which the arrangement of fingers also encodes the Christogram (IC XC — Jesus Christ in Greek abbreviation). The gold background places this figure outside time, in the eternal present of heaven.

Made after 1261, when the Byzantine emperor Michael VIII Palaiologos retook Constantinople from the Latin Crusaders who had occupied it for 57 years. The reconquest was celebrated as a miraculous restoration; the mosaics of Hagia Sophia, damaged or defaced during the Latin occupation, were systematically restored. Within two centuries, the Ottomans would convert the Hagia Sophia to a mosque and whitewash its mosaics. The Deësis was rediscovered in 1934.

The Pantocrator image traveled from Constantinople throughout the Orthodox world and directly influenced the development of the altarpiece and painted crucifix in medieval Italy. Cimabue's painted Christs of the late thirteenth century, and from there Giotto's, are in direct conversation with the Byzantine Pantocrator — arguing with it, humanizing it, learning from it.