Located in Istanbul’s old town on the European side of the Bosphorus, Hagia Sophia ("Holy Wisdom") was built in the 6th century and was the world's largest religious monument for nearly a thousand years. The building has multiple buttressed domes and towering minarets, and the interior features many intricate golden mosaics. The Ottomans turned Hagia Sophia into a mosque in 1453 when they took Constantinople. Now it is a public museum and a highlight of any visit to Istanbul. Take a tour with the slideshow above.