Big Bus Istanbul Hop-On Hop-Off Tour. Istanbul is one of the world’s greatest cities, and this hop-on hop-off Istanbul tour offers a truly flexible way to explore it. Choose a 24- or 48-hour pass, board your open-top, double-decker Istanbul hop-on hop-off bus at any stop along the two routes, and enjoy the views as you listen to the audio commentary. Then, create your own sightseeing itinerary as you hop on and off at any of the stops to visit highlights such as the spectacular Topkapi Palace, the UNESCO-protected Hagia Sophia, the Egyptian Bazaar and many more! Book Big Bus Istanbul Hop-On Hop-Off Tour From $34.40.