All trips to Istanbul should include a visit to the most famous Christian church in the world, the Hagia Sophia, located in the old town in front of the Sultanahmet Square. Combine this experience with a river cruise on the Bosphorus. From the boat, admire the city's most historic buildings and almost all seven hills. At the Hagia Sophia, meet a local host who will take you through a fast-track line to enter the site, followed by a short security check. Once inside, explore the gardens and admire the monumental architecture of the building which was reinforced during the Ottoman Era. Enter the building through the main gate and marvel at the frescoes in the first hall. Check out the second floor to see the original frescoes of the Orthodox church and even a mark made from a viking intruder on the wall. Begin either with the cruise or from the Hagia Sophia. Your local host will help you get oriented and advise you of the best time to visit both attractions so as to avoid long lines. You may use the same voucher for both experiences, even on two consecutive days. Please note that you can easily walk from the meeting point to the pier.  The cruise lasts a bit less than two hours and takes you along the Bosphorus and inside the Golden Horn. While on the boat, take photos of the whole city and admire important monuments and mosques from a distance. The boat will return to its departure point and then you are free to walk back to the old town center.