Hagia Sophia, Constantinople / Istanbul

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The great church of Holy Wisdom, built for Justinian I between 532 and 537 to designs by Anthemius of Tralles and Isidore of Miletus, and dedicated on 27 December 537. Its structural claim is not size but geometry: it puts a circular dome about 31 m across on a square bay by means of pendentives, and then buttresses that dome longitudinally with two enormous half-domes so that the interior reads as a single flowing space rather than a rotunda. The first dome was shallow, and after earthquakes it fell in May 558; Isidore the Younger rebuilt it steeper - raising the crown by roughly six metres and so reducing the outward thrust - and the rebuilt dome was dedicated on 24 December 562. It has partially collapsed and been repaired again since, in the 10th and 14th centuries. The building was a church for nearly a millennium, an Ottoman mosque from 1453, a museum from the 1930s, and was reconverted to a mosque in July 2020. It stands within the UNESCO World Heritage property Historic Areas of Istanbul.