Most visitors spend at least three days in İstanbul and cram as many museum visits as possible into their stay, so purchasing a Museum Pass İstanbul (http://www.muze.gov.tr/en/museum-card) is worth considering. Valid for 120 hours (five days) from the first museum you visit, it costs ₺85 and allows one entrance to each of Topkapı Palace and Harem, Aya Sofya, Aya İrini, the İstanbul Archaeology Museums, the Museum of Turkish and Islamic Arts, the Great Palace Mosaics Museum, the Kariye Museum (Chora Church), Galata Mevlevi Museum, Fethiye Museum, Rumeli Hisarı and the İstanbul Museum of the History of Science & Technology in Islam. Purchased individually, admission fees to these sights will cost ₺250, so the pass represents a possible saving of ₺165. It sometimes allows you to bypass ticket queues too.
As well as giving entry to these government-operated museums, the pass also provides discounts on entry to privately run museums such as the Museum of Innocence, the Pera Museum and the Rahmi M Koç Museum.
The pass can be purchased through some hotels and from the ticket offices of all of the museums it covers.