Completed in Constantinople (modern Istanbul) in 537 AD under Emperor Justinian I, Hagia Sophia held the title of the world's largest cathedral for close to a thousand years, and its huge dome was the largest of its kind for centuries. It later became a mosque, then a museum, and functions as a mosque again today.
Record no. MRB-2026-005742
World's Largest Cathedral for Nearly a Millennium
Reference Record – Not Certified
This record is compiled from publicly available sources for reference. It has not been examined or certified by The Book of World Records.