Once a church, then a Byzantine cathedral, later a mosque and now a monument, this iconic building is a national treasure.
This collection of historical artifacts in Sultanahmet is well-liked by many travelers, so be sure to put it on your to-do list. Don't think the sightseeing ends there, however. There are a lot more spots waiting for you to enjoy after Hagia Sophia. Blue Mosque, Topkapi Palace, and Basilica Cistern are nearby.