Two temples in Istanbul. Hagia Sophia has 78 tickets and tours to book; Sultan Ahmed Mosque (Blue Mosque) has 34 tickets and tours to book. The table and the two notes below put them side by side; the full pages have what to see, the ticket and the timing for each.
Since Hagia Sophia became a mosque again in 2020, the way you visit it has changed. Worshippers enter free to the prayer hall on the ground floor, while foreign visitors buy a ticket for a separate route through the entrance hall and up to the upper galleries, from which you look down into the main space. The ticket is sold at the site and online, and the queue at the entrance can be long, especially in the middle of the day.
What is sold online falls into a few groups. Fast-track tickets save the queue for the ticket, though not always the security check. Guided tours of the building last about an hour and are worth considering here more than at most mosques, because the story of the building is complex and the signage is sparse.
Entry to the Sultan Ahmed Mosque is free and there is no ticket to buy, so anything sold online is really a guide, a combination with paid sights next door, or both. Visitors simply queue at the tourist entrance on the Hippodrome side, which moves fairly quickly outside the busiest hours, and the mosque closes to sightseers during each of the five daily prayers.
The most common product is a guided walk of the Sultanahmet quarter, usually two to four hours, that takes in the mosque, the Hippodrome with its obelisks and the exterior or interior of Hagia Sophia. Longer versions add Topkapi Palace and its Harem, the Basilica Cistern or the Grand Bazaar, and full-day tours often finish with a Bosphorus cruise;