To see most of Istanbul's top museums in a short time, with reduced admission fees and shorter waiting lines, you may want to buy a Museum Pass Istanbul.
The 5-day pass is sold for TL125 and is valid for one entrance to these museums within 120 hours after the first use of the pass to enter a museum:
—Topkapı Palace (Harem optional for TL25 more, Hagia Eirene [Aya Irini] for TL20 more)
—Istanbul Archeological Museums
—Istanbul Great Palace Mosaic Museum
—Museum of Turkish & Islamic Arts
—Museum for the History of Islamic Science & Technology in Gülhane Parkı
—Chora Church Museum (Byzantine Mosaics)
—Galata Mevlevihanesi (Whirling Dervish Hall)
—Rumeli Hisarı Fortress
—Istanbul Fethiye Museum (Pammakaristos Church)
Considering that entry to Topkapı Palace costs TL40, and to Hagia Sophia another TL40, and that the other museums have entry fees of TL20 or more, if you visit the top museums and one more, you've paid for the pass.
Note that there is also an All-Turkey Museum Pass for TL210 which gives you admission to 300+ museums operated by the Ministry of Culture and Tourism for 15 days, but remember: not all museums are operated by the Ministry. Museums outside the Ministry's control may not be included in the pass. More...
Regional Museum Passes are also sold for Cappadocia, the Aegean region and the Mediterranean coast. More...
In addition to admission to those museums, the pass entitles you to discounts at numerous other museums, attractions, travel companies and shops including Efendi Travel, Şehir Hatları ferryboats, Orhan Pamuk's Museum of Innocence (Masumiyet Müzesi), Harbiye Military Museum, Pera Museum, Rahmi M Koç Museum, Sakip Sabancı Museum, Sadberk Hanım Museum, and more.
Saves You Time
Although the Istanbul Museum Pass allows you to avoid waiting in the ticket-purchase line at each museum, it does not exempt you from the security-check line, so you will still have to spend time waiting in line, meaning that the time it takes you to visit a museum is not just the time you enjoy inside the museum.
Plan Your Museum Visits
Because certain of these museums are closed on different days, you should plan your days carefully:
For example, if you entered your first museum on Saturday morning, you should plan to visit on Saturday and Sunday all of the museums that are closed on Monday, leaving Topkapı Palace to be visited on Monday.
And if you start your pass by entering Hagia Sophia on Tuesday morning, you cannot continue your sightseeing at Topkapı Palace, right next to Hagia Sophia, because Topkapı is closed on Tuesday.
Start Around Noon
Here's a tip: you can have 6 calendar days of museum visits by initiating your pass around 12 noon or 13:00/1pm so that it is valid for that afternoon, the next full days, and the morning of the final day.
Thus, if you validate your pass with a visit to one museum in the afternoon of Day 1, visit any museums you like all day on Days 2, 3, 4 and 5, you can still visit a museum on the morning of Day 6 before the pass's validity ends at 12 noon or 13:00/1pm.
Start Your Pass at Chora Church
Another tip: except on Wednesday (when it's closed), start your pass at the Chora Church/Kariye Museum because it's farther from the center. Go to the neighborhood of the museum in the morning, visit the lovely Mihrimah Sultan Mosque, the Palace of Constantine Porphyrogenetus and the City Walls, have a bite of lunch, and then enter the Chora, starting the pass clock running. Why have the clock running while you're in a bus or taxi traveling to the Chora? Most of the other museums are closer to Sultanahmet.
Remember, your pass becomes valid the first time to use it to enter a museum, and may be used to enter any or all of the other museums included in the program, but only for one entry per museum—you can't leave the museum and re-enter on the same pass, even on the same day, even if your pass's validity is still current.
Note Last-Entry Times
Entry to museums ends 30 minutes before the daily closing time (so if closing time is 17:00/5 pm, you will not be allowed entry after 16:30/4:30 pm). Thus if you enter at 16:29/4:29 pm, you'll have only a half hour to tour the museum on your pass. You cannot do "half a visit" to a particular museum on one day, and come back to that same museum the next day to see the rest, at least not using the pass (though you can always wait in line and purchase a regular ticket if you wish.)
And in Hagia Sophia, the all-important upper-level gallery with the wonderful mosaics closes 30 minutes before the museum's closing time—another good reason to start the pass's clock in the afternoon on Day 1, so your final hours will be in the morning of your final day, with no fear of an early closing.
Where to Buy Istanbul Museum Passes
The Istanbul Museum Pass is sold at all of the museums mentioned above (unless they run out of cards the day you're there, which can happen); online; at automated kiosks and mobile sales vehicles near museums (if you can find them, and if they aren't out of order); and at many hotels including these recommended by TurkeyTravelPlanner.com:
—by Tom Brosnahan