Ayasofya or Hagia Sophia was initially built as a church under the Latin Empire, but it was converted into mosque after Fatih Sultan Mehmed ruled Istanbul. Afterwards, it was used as a mosque for 482 years. Under the order of Atatürk, Hagia Sophia was converted into a museum in 1935.
The museum is located directly the opposite of Sultanahmet Mosque. So after visiting the Sultanahmet Mosque or Blue Mosque, I could walk over about 5 minutes. Going inside the museum, I was welcomed by chandeliers and felt as if I were in Harry Potter’s World :p
The unique thing about Hagia Sophia is that the interior of church still remains although it was ever changed its function as a mosque. Only the bells, altar, iconostasis, and sacrificial vessels and other relics were removed and the paintings of Jesus, his Mother Mary, Christian saints and angels were also removed or plastered over.