Rowland Mainstone's architectural study of Hagia Sophia traces how its builders solved the problem of covering a vast square space with a round dome using pendentives, curved triangular sections that translate the dome's circular base onto the four supporting arches beneath it, a solution so influential it became the standard method for large domed construction across the later Byzantine and Ottoman worlds. Ottoman architects, including the great Mimar Sinan, studied the building directly and built Istanbul's imperial mosques in deliberate conversation with it, so much of the city's skyline exists in visual dialogue with Justinian's original.
The interior still carries both traditions' devotional art in the same space: ninth and tenth century mosaics depicting Christ Pantocrator, the Virgin and Child, and Byzantine emperors were plastered over after the 1453 conversion in keeping with Islamic prohibitions on figural imagery in a mosque, then partially uncovered during the museum era, and remain visible today alongside the Ottoman calligraphic medallions and mihrab, covered during prayer rather than removed since the 2020 reconversion.
The 2020 decision to restore active mosque status drew a sharply divided response: welcomed within Turkey as a restoration of Ottoman and Muslim heritage, and criticized by UNESCO, the government of Greece and some Christian communities on grounds ranging from World Heritage protections to interfaith relations. This atlas records the building's full layered history, Byzantine cathedral, Ottoman mosque, secular museum, and mosque again, and its current active status, without adjudicating the 2020 decision's merits.