Completed in 537 CE under Emperor Justinian I, Hagia Sophia’s revolutionary ribbed dome crowned the Byzantine capital for nearly a millennium. Converted to a mosque in 1453, it gained minarets and calligraphy; in 1935 it became a museum, and in 2020 reconverted to a mosque. Ongoing conservation balances mosaics, marbles, seismic safety, and visitor access at one of the world’s most contested, influential sacred spaces.
After the Nika riots devastated Constantinople in 532, Justinian I ordered an unprecedented church. The geometers Isidore of Miletus and Anthemius of Tralles designed a vast square naos crowned by a 31–32 m radius dome on pendentives. Four colossal piers take the thrust to foundations; semi‑domes buttress to east and west. A lightweight brick and mortar mix and a ribbed, segmental profile reduce mass while windows at the dome’s base create the famed “crown of light.”
Proconnesian marble revetments, spolia columns, porphyry and green Thessalian marbles animate surfaces with veined symmetry. The floor’s opus sectile patterns guide procession; gold‑ground mosaics—Christ Pantocrator, Theotokos, imperial panels—develop over centuries. Acoustics are long and resonant; liturgy once amplified by curtains and metal fittings.
The original dome partly collapsed in 558, prompting Isidore the Younger to rebuild with a steeper curvature and heavier ribs, raising the crown. Subsequent earthquakes led to chains, buttressing, and vault repairs. Ottoman architects (notably Sinan) added external buttresses and minarets; iron ties and timber struts controlled spreading.
Following 1453, Hagia Sophia became Ayasofya Camii: mihrab and minbar were added, figural mosaics were plastered over (not always destroyed), and calligraphic roundels by Kazasker Mustafa İzzet Efendi adorned the nave. In 1935 it became a museum, enabling scientific uncovering of mosaics by the Byzantine Institute.
The 2020 reconversion to a mosque reactivated worship while retaining broad visitation. Protective curtains and lighting aim to shield mosaics during prayers. Conservation priorities: dome/fly buttress monitoring, mortar compatibility, micro‑climate control for marbles and tesserae, and crowd management for millions of visitors yearly.
Early mornings outside peak season reduce queues. Look for the Deësis mosaic in the south gallery and the marble “sweating column.” Pair with the nearby Blue Mosque for a comparative study of dome‑and‑semi‑dome spaces.
