The Turkish Ministry of Culture and Tourism has announced new rules for visiting Hagia Sophia. The entrance for tourists has become paid. Entrance to the main hall remains free for all Muslims who wish to make prayer. For tourists, there is a separate entrance and the cost of visiting is 25 euros (including for Turkish citizens and for those who have a museum card). Admission is free for children under 8 years old. Women can only enter with their heads covered. An audio guide in 23 languages is available in the tourist part of the cathedral. All you need is a smartphone and headphones.
The Hagia Sophia was built in 537. In 1453, after the capture of Constantinople by the Ottoman Empire, it became a mosque. From 1934 until 2020, it was in the status of a museum. Now it's a mosque again.