Hagia Sophia is Istanbul’s monumental former cathedral turned mosque, standing as one of the world’s most significant architectural landmarks. Built in 537 AD under Byzantine Emperor Justinian I, it was the largest cathedral in the world for nearly a thousand years before being converted into a mosque after the Ottoman conquest of Constantinople in 1453, and reconverted into a working mosque in 2020 after serving as a museum.
Inside, visitors can admire soaring Byzantine domes, Christian mosaics that survived centuries of change, and Islamic calligraphy medallions, a rare architectural blend spanning both faiths. The upper galleries offer some of the best views of the vast interior.
Hagia Sophia is open daily from 9 AM to 7 PM, with last entry at 6:30 PM, though it closes to tourists from noon to 2:30 PM on Fridays for weekly prayers. Early morning at opening or after 5 PM are the quietest times, and spring and autumn bring the most pleasant weather.