The Hagia Sophia is a must-see exhibit. there are many people lining up at the entrance. if you have credit-card,best to use credit card at the machine to buy ticket and avoid the wait . the admission is 72 Turkish Lira. dont forget to visit the 5 tomes of the Sultans, located ‘to the left after exiting the Hagia Sophia’. the entrance to the tomes are free, but must remove shoes prior to entrance of each tome.