Key facts
Hagia Sophia stands in the historic Sultanahmet district of Istanbul and ranks among the most significant buildings in architectural history. Built as a Byzantine church, converted into a mosque after the Ottoman conquest, run as a museum through the 20th century, and now a mosque again, it embodies layers of religious and cultural change. Its long life makes it a rare witness to the city's shifting identities. Few buildings anywhere have served three major faiths under one roof.
When was Hagia Sophia built and by whom?
The current structure was commissioned by Byzantine Emperor Justinian I and built between 532 and 537, opening for worship on December 27, 537. Its architects were the mathematician Anthemius of Tralles and the engineer Isidore of Miletus. It was the third church raised on the site after two earlier buildings were destroyed. The site had already held two earlier churches, both lost to fire and unrest, including the Nika riots of 532 that razed the second building.
What makes its architecture so important?
Hagia Sophia was among the first large-scale buildings to successfully carry a dome on pendentives, a technical breakthrough that shaped later church and mosque design across the region. The dome spans roughly 33 meters and, at completion, enclosed one of the largest interior spaces in the world at the time. After partial collapse following the earthquake of 558, the dome was rebuilt at a greater height. In the 16th century, the Ottoman architect Mimar Sinan reinforced the structure with external buttresses, and its dome-and-pendentive design went on to influence later imperial mosques such as the Süleymaniye.
How did its function change over the centuries?
Following the Ottoman conquest of Istanbul in 1453, Hagia Sophia was converted into a mosque and four minarets were added over time. In 1935 the Turkish Republic turned it into a museum, displaying its Byzantine and Ottoman heritage side by side. Since 2020 the building has again functioned as a mosque, though visitors can still view its mosaics and calligraphy inside. The four minarets were not built at once — they were added gradually by different sultans over roughly a century, giving the exterior its familiar silhouette.
What can visitors see inside?
Inside, visitors find gold-ground Byzantine mosaics, monumental calligraphic roundels, marble columns, and the sweeping expanse of the dome overhead. The building has been part of the UNESCO World Heritage-listed Historic Areas of Istanbul since 1985. Because it functions as an active mosque, modest dress and respectful conduct are expected, and current visiting rules should be checked locally. Look for the Deësis mosaic and the images of emperors and empresses in the upper galleries, along with the circular marble panel on the floor once used for imperial coronations.
What should you know before visiting Hagia Sophia?
Hagia Sophia sits on Sultanahmet Square within walking distance of Topkapı Palace and the Blue Mosque, making it easy to combine with a walk through the old city. Its dual religious and museum history means photography and movement inside are subject to specific rules. Opening hours and entry conditions change, so confirming details through official sources before your visit is worthwhile. Because it remains an active place of worship, some areas may be closed to non-worshippers during prayer times.
