Hagia Sophia

Hagia Sophia is a great architectural beauty and an important monument both for Byzantine and for Ottoman Empires. Once a church, later a mosque, and now a museum at the Turkish Republic, Hagia Sophia has always been one of the most precious of its time. Istanbul has hosted many civilizations for centuries, with which Byzantium and Ottoman Empires were the most famous. The city today carries the characteristics of these two different cultures and undoubtedly Hagia Sophia is a perfect synthesis where one can observe both Ottoman and Byzantium influences under one great dome.

(Side note: St. Peter's Basilica was built 900 years after completion of Hagia Sophia.)