- SULTANAHMET area is probably the area which is on the list of 99% of tourists which visit Istanbul. It is a heart of old Byzantium and later also Ottoman state. Many museums there are quite expensive, yet worth to visit: like Hagia Sofia and Topkapi palace. However, some nice and less known museums and mosques have no addmission fee. I would suggest you to visit the famous Blue mosque (Sultanahmet mosque) and Küçük Aya Sofya (or little Hagia Sofia) mosque. Also you can visit beautiful Gülhane park and first gardens of Topkapi palace.